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ELEMENTS OF MODERN CHEMISTRY. 







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ELEMENTS 



OF 



MODERN CHEMISTRY, 



BY CHAELES ADOLPHE WURTZ. 



SIXTH AMERICAN EDITION, 



REVISED AND ENLARGED BY 

WM. H. GEEENE, M.D., 

AND 

HAERY F. KELLEE, Ph.D. (Steasburg). 



WITB. A PORTRAIT OF THE AUTHOR AND NUMEROUS ILLUSTRATIONS. 



PHILADELPHIA: 

J. B. LIPPINCOTT COMPANY. 

London: 36 Southampton Street, Covent Garden. 

1900. 



63714 



L.iaetA.s f o1 Ooni.fr««* 



pVsU CoPtU REC£i*EO 

! OCT SO 1900 

I Copynght «ntry 

SLCPNO COPY. 

Oeiivered to 

OROEt) DiVISION, 

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Copyright, 1879, by J. B. Lippincott & Co. 



Copyright, 1895, by J. B. Lippincott Company. 



Copyright, 1898, by J. B. Lippincott Company. 



Copyright, 1900, by J. B. Lippincott Company. 



Electrotyped and Printed by J. B. Lippincott Company, Philadelphia, U.S.A. 



BIOGMPHICAL SKETCH. 



Charles Adolphe Wurtz, the most illustrious French 
chemist of the latter half of the nineteenth century, was 
born at Strasburg, November 26, 1817, and died at Paris, 
May 12, 1884. 

Early in life his tastes led him to scientific studies, and 
he became a student of medicine under the Faculty of Medi- 
cine of Strasburg, in which he was appointed Director of 
Chemistry in 1839. After acquiring the degree of Doctor 
of Medicine, he continued his chemical studies under the 
direction of that foremost of chemical teachers, Liebig, at 
Giessen : here he became intimately associated with such 
men as Strecker, Will, Fresenius, Hofmann, and Hermann 
Kopp, many of whom were destined later to make world- 
wide reputations in the same field with himself. 

In 1844 he removed to Paris, entering the laboratory of 
the celebrated Dumas, to whom he became assistant the fol- 
lowing year. Besides this position, he filled that of Director 
of Chemistry in the Ecole Centrale des Arts et Manufactures 
from 1845 to 1850, and in 1847 was chosen Professor agrege 
at the Paris Ecole de Medecine, in which he became Pro- 
fessor of Chemistry in 1853, retaining this post until his 
death. In 1866 he was chosen Dean of the Faculty, at that 
time troubled by political dissensions which his tact and 
judgment were well adapted to calm. He took advantage 
of his administrative position to strengthen and improve the 
scientific lines of the curriculum, and when he resigned the 
deanship, in 1874, he had succeeded in establishing a Chair 

5 



b BIOGRAPHICAL SKETCH. 

of Organic Chemistry in the Sorbonne and a laboratory of 
Biological Chemistry in the Medical School. 

In 1858, Wurtz founded the Societe Chimique de Paris, 
to which he presented many of his papers. In 1867 he was 
made a member of the Academy of Sciences (Institute de 
France), and was chosen president of the same in 1880. 

He was a brilliant and lucid teacher, an eloquent speaker, 
and he possessed in a remarkable degree the faculty of in- 
spiring his audiences with his own enthusiasm. 

Wurtz's chemical work was accomplished with very modest 
experimental means, and his aim was always rather to sim- 
plify than to complicate. His main researches were under- 
taken with the object of developing the atomic theory, then 
just beginning to be understood, and while these works 
covered an extensive field, they are, as A. W. Hofmann has 
well expressed it, " linked together like the pearls of a neck- 
lace." His results led him to support enthusiastically the 
theory of which he became the greatest if not the first 
champion in France. 

The best known of Wurtz's writings are his "Atomic 
Theory," published in the International Scientific Series, his 
" Elementary Lessons," and his " Dictionnaire de Chimie," 
published with the collaboration of a number of eminent 
French chemists. He also wrote a Medical and Biological 
Chemistry in three volumes. 

Among the more important of his chemical researches 
were those on the constitution of the acids of phosphorus, 
on the cyanuric ethers, compound ammonias, ureas, amides, 
and glycerol ; in the course of these he discovered the 
glycols, oxide of ethylene, aldol and paraldol, and hydride 
of copper, as well as the correct explanation of certain in- 
teresting cases of anomalous vapor density. 



ATJTHOE'S PEEFAOE 

TO THE 

FIRST AMERICAN EDITION. 



This book is translated from the fourth French edition by 
my pupil and friend, M. Grreene, whose perfect familiarity with 
the French language and thorough competence, at the same 
time, in chemistry I have had occasion to appreciate. The 
translation is, then, a faithful, or even improved, representation 
of the original work, in which he will certainly have detected 
and corrected some faults. 

The French editions succeed each other rapidly, showing 
that this little book responds to an educational need. 

It has been the endeavor to keep it up with the current of 
the latest discoveries, and in it to condense a considerable 
number of exact and well-selected facts, without banishing the 
theory which binds them together. Thus, the origin and foun- 
dation of the atomic theory have been given, as far as possible, 
in historical order. The notions concerning atomicity, so im- 
portant for the appreciation of the structure of combinations 
and for the interpretation of chemical reactions, are presented 
in an elementary form. 

The reader will remark that the history of the metalloids 
is relatively more developed than the remainder of the book. 
Indeed, this is the fundamental part of chemistry, and a fa- 
miliar knowledge of it is indispensable to the fruitful study of 
the metals and of organic chemistry. It is also the most at- 
tractive portion for beginners, for it is the most easily under- 
stood. 

Immediately on entering the immense domain of organic 

7 



o AUTHOR S PREFACE. 

chemistry, wc find the facts overwhelmingly numerous and 
complicated. Among all these facts a severe and careful 
choice has been made, the historical importance and the theo- 
retical and practical interest of the compounds described being 
borne in mind. In this respect many additions have been 
made to the third French edition. Thus, the question of 
isomerism, upon which the theory of atomicity has thrown so 
much light, has been treated in a more thorough manner. 
The chapter on the aromatic compounds has been considerably 
augmented. 

The author hopes that these " Elementary Lessons" will be 
well received by the new public to whom they are presented, 
and that they will contribute to render attractive and diffuse 
the knowledge of the science to which he has devoted his life. 

ADOLPHE WURTZ. 

Paris, November 20, 1878. 



The progress of the science has made necessary many changes 
in the fifth edition of this little book, which has so far retained 
about the form and scope given to it fifteen years ago. It has 
been deemed advisable to complete the organic portion, and a 
large number of additions and corrections have been made. 
Whole chapters have been added to the history of the cyanogen 
compounds, the hydrocarbons, the acids, and the aromatic com- 
pounds. Among these will be particularly noticed the articles 
on isomerism, the azoic and diazoic compounds, and the pyridic 
bases, subjects which have acquired great importance during 
the last few years. 

Paris, 15tli September^ 1883. 



PEEFAOE TO NEW EDITION. 



The considerations wliich guided tlie American editors in 
the preparation of the fifth edition, have been followed also 
in the revising of the book for this new edition. Besides 
making numerous corrections and additions which were ren- 
dered necessary by the rapid advance of the science, the 
editor has endeavored to eliminate terms and symbols which 
are no longer generally current, or which betray the French 
origin of the work. A new chart showing the spectra of the 
principal gaseous elements, as well as those of metals, is sub- 
stituted for that found in the former editions. 

*r H. F. K. 

Philadelphia, September 16, 1900. 



PEEFAOE, 



Sixteen years ago this translation of Wurtz's " Legons 
elementaires de Chimie Moderne" was first presented to the 
public by one of the present editors. The hearty favor with 
which the book was received by American and English 
chemists, and the fact that it has now undergone the fifth 
revision, are sufficient indications of its usefulness. 

In the preparation of the present edition, the aim has 
been to preserve as nearly as possible the original plan and 
character of the work, but at the same time to make such 
changes as will entitle it to continue to rank as a truly 
modern text-book. In order that this might be accomplished 
with the least possible enlargement, some matters of minor 
importance in an elementary treatise have been omitted, and 
the new matter which has been introduced will, it is believed, 
be found to include the latest developments of the science. 

A number of the original illustrations have been replaced 
by more modern designs, but in not a few instances it has 
been deemed desirable to retain cuts, which, while they do 
not represent the newest forms of apparatus, are yet of great 
historical value in illustrating the development of chemical 
experimentation. 

To meet numerous requests, mention has been made of 
many matters that are of special interest to the student of 
medical chemistry. 

W. H. G. 
H. F. K. 



TABLE OF CONTENTS. 



Introduction — Distinction between Chemical and Physical Ac- 
tion . • . . . 



Definition of Chemistry ... 

Affinity — Molecules — Atoms 

Chemical Combination .... 

Decomposition — Double Decomposition , 

Law of Definite Proportions — Equivalents 
tions 

Hypothesis of Atoms .... 

Gay-Lussac's Law — Atomic Theory 

Ampere's Law — Avogadro's Law . 

Law of Specific Heats . . o . 

Law of Isomorphism — Nomenclature and Notation 

Table of Elements and Atomic Weights 

Binary Oxygen Compounds .... 

Oxygen Acids and Metallic Hydroxides 

Oxygen Salts 

Nomenclature of Non-Oxygenized Compounds 

Alloys and Amalgams 

Hydrogen 
Oxygen 
Ozone . 



Multiple Propor- 



Air 

Argon 

Water 

Mineral Waters 

Sulphur 

Hydrogen Sulphi 

Hydrogen Persulphide 

Oxygen Acids of Sulphur 

Sulphur Sesquioxide — Sulphur Dioxide 

Hyposulphurous Acid — Sulphur Trioxide 

Sulphuric Acid . , , , , 



PAGE 

ir-19 
. 20 
21-23 

24-27 
27-30 

31-36 

. 36 

. 37 

40-42 

44 

47 

49 

50 

52 

53 

56 

57 

58 

64 

69 

73 

77 

80 

92 

98 

102 

105 

106 

107 

110 

111 



H 



12 TABLE OF CONTENTS. 



PAGE 

Pyrosulphuric Acid 118 

Thiosulphuric Acid ..... c ... . 119 

Persulphuric Oxide , . . . 120 

Selenium and Tellurium 121 

Chlorine 122 

Hydrochloric Acid 126 

Hypochlorous Oxide and Acid 132 

Chlorine Peroxide . . , . 134 

Chloric Acid — Perchloric Acid 135 

Chloride of Sulphur . . . . . . . . . ,136 

Bromine 137 

Hydrobromic Acid 138 

Hypobromous Acid . . , 139 

Bromic Acid — Perbromic Acid — Iodine ...... 140 

Hydriodic Acid ,...., 142 

Iodine Oxides and Oxygen Acids . . . . . . . 144 

Periodic Acid 145 

Analogies of Chlorine Group . 145 

Fluorine ............ 146 

Hydrofluoric Acid .....,. = ., 147 

Nitrogen ..... 148 

Ammonia ............ 149 

Nitrogen Chloride . . . 154 

Nitrogen Iodide — Ammonium Amalgam , 165 

Ammonium Chloride . . 156 

Ammonium Hydrosulphide and Sulphide . . , . . .157 
Ammonium Nitrate . . . , . . . . . .158 

Ammonium Carbonate . , , . 158 

Ammonium Sulphate . . . . . . . . , .159 

Hydroxy lamine . , . . . , . , , . .159 
Hydrazine — Hydrazoic Acid — Oxygen Compounds of Nitrogen . 160 

Nitrous Oxide . 161 

Nitric Oxide 163 

Nitrogen Trioxide , . . , . . . . . .164 

Nitrogen Peroxide — Nitryl Compounds . . „ . . 165, 166 

Nitrogen Pentoxide — Nitx'ic Acid . 167 

Nitro hydrochloric Acid . . . , . , . . .170 
Phosphorus . . . - . . . . . . ,171 

Phosphine ,.......,.,.. 175 

Phosphorus Trichloride — Phosphorus Pentachloride .... 178 

Phosphorus Oxychloride — Compound of Phosphorus with Bromine, 

Iodine, and Fluorine ....... 179, 180 

Compounds of Phosphorus and Oxygen 180 

Hypophosphorus Acid ......... 181 

Phosphorus Acid 182 

Phosphoric Oxide — Phosphoric Acid ,....., 183 

Pyrophosphoric Acid ,,.,...... 184 

Metaphosphoric Acid ......... 185 

Phosphorus and Sulphur— Arsenic ....... 186 

Arsine ............ 188 

Arsenic Chloride, Bromide, and Iodide — Arsenious Oxide . . . 189 
Arsenic Acid ........... 192 

Arsenic Sulphides ..,,,.... 193, 194 



TABLE OF CONTENTS. 13 

PAGE 

Antimony 195 

Stibine .196 

Antimonous Oxide — Antimony Antimonate 198 

Antimonic Oxide and Acids — Antimony Sulphides . . . 199, 200 

Analogies of Nitrogen Group 200 

Boron 201 

Boron Chloride 202 

Boron Fluoride — Boric Acid 203 

Silicon ............ 204 

Hydrogen Silicide 205 

Silicon Chloride 206 

Silicon Fluoride . . . . 207 

Silica . . . , . 208 

Carbon ..... 209-215 

Carborundum — Compounds of Carbon and Oxygen . . . .216 

Carbon Monoxide .......... 217 

Carbonyl Chloride — Carbon Dioxide . , . , . . .219 

Carbon Bisulphide 225 

Carbon Oxysulphide .......... 226 

Compounds of Carbon and Hydrogen 227 

Flame 228-231 

Theory of Atomicity 232 

Chemical Energy — Thermo-Chemistry 240 

General Properties of Metals 243 

Natural State and Extraction of Metals ...... 247 

Alloys 248 

Oxides and Metallic Hydroxides ...... 250-257 

Sulphides , 257 

Chlorides 258 

Salts ............. 262 

Richter's Laws - , , , . . o . . . . 265 

General Properties of Salts , w . , . , . . 267 

Supersaturation . . . 271 

Electrolysis 274 

Arrhenius's Theory — Faraday's Law 276 

Berthollet's Laws 277 

Nitrates . , 283 

Sulphates 285 

Carbonates 287 

Classification and Atomicity op Metals 289 

Mendelejepp's Periodic Law 294 

Potassium ....,, 297 

Sodium ............ 306 

Lithium — Caesium and Rubidium — Spectrum Analysis . . . 315 

Silver and its Compounds 317 

Calcium 324 

Strontium ............ 330 

Barium ............ 331 

Glucinum 333 

2 



14 TABLE OF CONTENTS. 



PAOB 

Magnesium 334 

Zinc 337 

Cadmium ............ 342 

Lead 343 

Copper . . 354 

Mercury ..,,.,...... 362 

Vanadium ....;.,. 370 

Niobium and Tantalum . . .' 371 

Gold . . .373 

Bismuth .,...,. 377 

Aluminium _........... 380 

Cerium, Lanthanum, and Didymium ...... 385 

Gallium . , , 386 

Indium , 387 

Rare Earths 388 

Iron . . . , 389 

Cobalt 401 

Nickel 403 

Manganese 405 

Uranium — Helium .......... 409 

Chromium . ........... 410 

Molybdenum — Tungsten 414 

Tin . . 416 

Titanium 421 

Germanium — Zirconium . . 422 

Thorium 423 

Platinum , 424 

Metals of the Platinum Group 427 

Organic Chemistry — Constitution of Organic Compounds . . 429 

Formation of Hydrocarbons 433 

Homologous Bodies — Chemical Species 435 

Elementary Analysis 436 

Determination of Molecular Weight ....... 440 

Determination of Melting and Boiling Points 444 

Isomerism 445 

Functions of Organic Chemistry 447 

Monatomic Radicals 448 

Polyatomic Radicals 469 

Cyanogen Compounds 462 

Compounds of Carbon Monoxide 473 

Monatomic Alcohols and their Derivatives — Methyl Compounds . 483 

Ethyl Compounds 497 

Series of saturated Hydrocarbons 517 

Petroleum 519 

Higher monatomic Alcohols 520 

Compound Ammonias 530 

Hydrazines . 532 

Phosphi'nes • 536 

Organo-metallic Compounds 539 

Fatty Acids . 541 

Formic Compounds 543 

Acetic Compounds ... 545 

Other Acids of the Series C^^H^nO' . . . '. . . .669 



TABLE OF CONTENTS. 15 

PAGE 

Oleic Acid and its Homologues 566 

Diatomic Hydrocarbons 568 

Hydrocarbons C°H2n-2 . 575 

Glycols and their Derivatives 577 

Glycerol and its Ethers 586 

Natural Fats 590 

Soaps — Polyatomic and Polybasic Acids 593 

Uric Acid and its Derivatives 624 

Polyhydric Alcohols 633 

Sugars and Starches 635 

Fermentation 646 

Glucosides . 657 

Aromatic Compounds and their Constitution 662 

Benzene and its Derivatives . . . . . . . .671 

Phenol . 677 

Aniline . 683 

Diazobenzene Compounds 686 

Rosaniline and its Derivatives 689 

Dioxybenzenes , , 692 

Toluene and its Derivatives 697 

Xylenes and their Derivatives . 714 

Trimethylbenzenes and Isomerides , 716 

Terpenes and Camphors 718 

Unsaturated aromatic Compounds ....... 729 

Indigo and its Derivatives . 732 

Naphthalene 738 

Anthracene and Phenanthrene 741 

Furfurane, Thiophene, and Pyrrol . 745 

Pyridine and its Derivatives 747 

Quinoline 750 

Alkaloids 752 

Substitutes for Natural Alkaloids 769 

Albuminoid Matters, Proteids 770 

Products of Animal Disassimilation 782 



ELEMENTS OF MODERN CHEMISTRY. 



INTRODUCTION. 

The material objects surrounding us present striking and 
infinite differences. Sulphur is readily distinguished from 
charcoal, rock-crystal from flint, iron from copper, water from 
spirit of wine, and wood from ivory. It is known to all that 
these bodies differ not only in form, density, and structure, but 
also in their proper substance. They differ, too, in the changes 
through which they pass under the same conditions. When 
subjected to the action of heat they receive very differently the 
impression of that force. They become heated more or less 
quickly, and transmit the heat with greater or less rapidity 
throughout their own substance. A short bar of iron cannot 
be grasped in the hand by one extremity if the other be heated 
to redness ; under the same conditions a cylinder of charcoal 
may be handled with impunity. Communicate sufficient heat to 
water and it is converted into steam ; remove heat from it, and 
if the cooling be sufficient, it is frozen into ice. Spirit of wine 
requires less heat to become vaporized, and extreme cold to 
congeal it. If a magnet be placed among iron filings, they 
attach themselves in tufts around the two poles; on the con- 
trary, copper filings are indifferent to the magnetic attraction. 

Rock-crystal is transparent to light ; flint is opaque. These 
two bodies are unalterable by fire. They may be heated to red- 
ness in a furnace, but after the temperature has abated they 
will be found with their original characters unchanged. It is 
very different with the coal which we burn in our grates. This 
body disappears during the combustion, and leaves only a quan- 
tity of ashes. But it has not been destroyed, and its substance 
is found in entirety in a certain gas produced by the combus- 
tion. Like charcoal, sulphur is combustible, and is converted 
by burning into a gas, the suffocating odor of which is well 
known. 

Neither sulphur nor charcoal undergo any alteration when 
b 8* 17 



18 ELEMENTS OF MODERN CHEMISTRY. 

exposed to damp air ; it is not the same witli iron. In a moist 
atmosphere this metal experiences a striking and lasting change. 
Its surface becomes covered with rust and is no longer iron. 

In the forests, the leaves which fall and remain upon the 
moist soil are slowly consumed and disappear in the course of 
seasons. 

All of these changes, these phenomena, take place daily be- 
fore our eyes, and are familiar to all of us. On comparison, 
striking diiFerences are discovered between them : some are but 
passing, and do not affect the proper nature of the body. They 
are the results of forces which act at sensible distances, and 
which leave the body in its primitive state as soon as their 
action has ceased. A piece of soft iron is attracted by the 
magnet before contact is established, and when under the mag- 
netic influence, is capable of attracting other soft iron in its 
turn : the action of the magnet has made the iron itself mag- 
netic, but it immediately loses this property when the magnet 
is withdrawn ; and further, this momentary change in property 
has brought about no alteration in the intimate nature of the 
iron. It is found after the experiment in precisely the same 
condition as before. 

In the same manner, rock-crystal undergoes no change in its 
specific identity by the passage of a ray of light. Withdraw 
from the vapor of water the heat which has been communi- 
cated to it, and the liquid water is recovered with all its prop- 
erties. Restore to the ice the heat which was abstracted in its 
formation, and water is regenerated as before. This is charac- 
teristic of the changes produced by physical forces. Under 
the influence of such forces, bodies experience modifications 
more or less profound, more or less lasting, but which never 
affect their specific nature. 

But the iron which rusts undergoes a complete and lasting 
change in its properties and in its substance. The rust is no 
longer iron, and vainly would it be sought to isolate the metal 
by mechanical means, or to discover its presence by the aid of 
the most powerful microscopes. The metal has disappeared as 
such ; it has undergone a complete transformation ; it has be- 
come another body. It has attracted one of the elements of 
the air, oxygen, and has, moreover, fixed to itself the moisture 
of the atmosphere. These latter bodies, which differ from iron 
in substance, have intimately united with the metal itself, and 
the result of this union, of this combination as it is called, is 



INTRODTJCTION. 



19 



a new body, rust or hydrated oxide of iron. In this case tlie 
alteration is profound, the change is lasting ; the specific nature 
of the body is affected. This is characteristic of chemical 
action. 

In the same manner, when the charcoal and the sulphur are 
burned in the air, they attract oxygen and combine with it, 
forming two new bodies that are called carbonic and sul- 
phurous acids. 

These phenomena may be rendered more clear by simple and 
well-known experiments. 

Experiment 1. — A globe (Fig. 1) is filled with oxygen, a 
gas which constitutes one of the elements of the atmosphere, 
and which is eminently fitted to support combustion ; into it is 
plunged a morsel of charcoal lighted at one end ; immediately 
the coal glows with a brilliant light, the combination takes place 
actively, and the charcoal is rapidly consumed. But presently 
the light becomes paler, the combustion ceases, and the char- 
coal is extinguished. The oxygen is now nearly or quite con- 





FlG. 1. 



Fig. 2. 



sumed, and the globe is filled with another gas which is no 
longer oxygen, although it contains that oxygen. It contains 
also the matter of the charcoal which has disappeared, and 
these two bodies have combined to form a new body, which is 
carbonic acid. This latter will not support combustion, but, on 
the contrary, it extinguishes burning bodies. It is then a body 
having entirely new properties, and is formed by a chemical 
action. 

Experiment 2. — Into another jar filled with oxygen (Fig. 2) 
is plunged a spoon containing ignited sulphur. The combus- 



20 ELEMENTS OF MODERN CHEMISTRY. 

tion takes place with a beautiful blue flame, and in burning in 
the oxygen with so much energy, the sulphur unites with the 
gas and forms with it a new body, which is called anhydrous 
sulphurous acid. It is a suffocating gas, which extinguishes 
flame. It reddens, and afterwards bleaches, a solution of blue 
litmus poured into the jar. These are special properties which 
do not belong to the oxygen at first contained in the jar. They 
characterize a new body, the result of the combination of the 
isulphur with the oxygen, and formed by chemical action. 

Carbon, sulphur, and oxygen are simple hodies or elements. 
They are so called because from neither of them can more than 
one kind of matter be obtained. But when the charcoal in 
burning unites with the oxygen, the carbonic acid which re- 
sults from the union contains two kinds of matter, — carbon and 
oxygen ; and these two elements are united in such an intimate 
manner that the body which contains both does not resemble 
either carbon or oxygen : it is endowed with new properties 
which do not in any manner recall those of the elements which 
constitute it. In fact, it is a new substance, a compound body 
formed by the combination of the matter of the charcoal with 
the matter of the oxygen. 

Considering the preceding facts, we may give to chemistry 
the following definition : chemistry studies those intimate ac- 
tions of bodies upon each other which modify their natures 
and cause a complete and lasting change in their properties. 

Iron may be reduced to a fine powder. This may be mixed 
with sulphur itself reduced to powder, and if the mixture be 
sufficiently intimate, it will present neither the lemon-yellow 
color of sulphur nor the gray-black of finelj^-divided iron. 
Nevertheless, a homogeneous substance cannot be formed in 
this manner. If the powder be examined under the microscope, 
the particles of iron may be recognized disseminated among 
those of the sulphur, but the two are not merged together. 
By the aid of a magnet the iron may be separated. On the 
other hand, if the mass be thrown into water, the particles of 
iron will sink first to the bottom, while the lighter particles of 
sulphur remain in suspension. Thus, after having triturated 
the sulphur and iron together, not only can each substance be 
recognized in the mass, but they can be again separated by 
mechanical means. Here there has been no chemical action, 
but simply a mixture. If, however, this mixture be heated, 
the sulphur will first be seen to melt, , and afterwards the 



INTRODUCTION. 21 

whole mass will blacken and enter into fusion if the tempera- 
ture be sufficiently elevated. After cooling, it is perfectly ho- 
mogeneous, and neither iron nor sulphur can be recognized. 
Both have disappeared as such, and in their place is found a 
substance having new properties ; it is the sulphide of iron. 

They have disappeared, but their substance is not lost ; and 
it may be proved by experiment that the weight of the sul- 
phide of iron produced is exactly equal to the sum of the 
weights of the iron and the sulphur. The ponderable matter 
of the iron is then added to the ponderable matter of the sul- 
phur, and has formed with it a union so intimate that there 
results a new body, the smallest particles of which are per- 
fectly similar to each other and to the entire mass. This ex- 
ample and a thousand others that might be given prove that 
when bodies combine there is neither loss nor creation of mat- 
ter. The result of the combination, that is, the compound 
body, contains the whole of the substance and nothing more 
than the substance of the combining bodies. This is an essen- 
tial characteristic of chemical combination. 

The force which determines chemical combination is called 
affimty. It is important that this force be distinguished from 
another which is often opposed to it, and which is cohesion. 

In order to reduce to powder a solid substance, such as 
pyrites or sulphide of iron, it is necessary to overcome the 
resistance opposed by the particles of the mass to their separa- 
tion. This resistance is due to a special force, which brings 
and maintains in relation to each other the homogeneous par- 
ticles of the sulphide of iron, as indeed of all solid bodies. 
This is cohesion. The particles which are bound together by 
this force are not only those minute particles which are visible 
to the naked eye or under the microscope, and of which the 
most impalpable powder of a solid body is composed. Such 
particles still present a magnitude that can be measured ; they 
must be considered as little masses, so to speak, indivisible by 
the mechanical means at our command, but formed in reality 
of particles still smaller. These smallest particles of a solid 
body which are bound by cohesion are called molecules. They 
are not in immediate contact with each other. In a perfectly 
compact and homogeneous mass, such as sulphide of iron, the 
molecules do not touch each other. Between them exist 
spaces of considerable magnitude, compared to the real volume 
of the molecule. This idea must not be confused with that of 



22 ELEMENTS OP MODERN CHEMISTRY. 

porosity, which is caused by those accidental spaces which form 
visible pores in solid bodies. The intermolecular spaces are 
those which separate the molecules of a homogeneous and com- 
pact solid body, and physicists have further been led to believe 
that even in solid bodies the molecules are not perfectly immo- 
bile, but that they execute vibratory movements in the spaces 
which separate them, at the same time maintaining their own 
relative positions. 

If a solid body be heated, a part of the heat is employed in 
raising the temperature, another part serves to increase the 
distances which separate the molecules : the body expands in 
becoming heated. But, as the distances between the molecules 
increase by the action of the heat and the efi'ect of the expan- 
sion, the molecular attraction necessarily becomes more feeble. 
Cohesion is thus somewhat diminished, and if the heat be 
further increased, it may be so much diminished that the mole- 
cules, which have thus far been maintained in definite rela- 
tions, can move and glide freely over each other ; the solid 
body then enters into fusion : it becomes a liquid. The liquid 
state is produced by a diminution of cohesion, and is charac- 
terized by a greater mobility of the molecules. 

But if the liquid body be still further heated, at a certain 
point the additional heat may produce such a separation of the 
molecules that, already freed from all mutual attraction, they 
become completely independent of each other. This is char- 
acteristic of the gaseous state. 

It may be stated, then, that cohesion is considerable in solid 
bodies, but slightly energetic in liquids, and null in gases, and 
we have just seen that heat, by causing the changes of state of 
a body, can overcome and even practically abolish this physical 
force. 

Chemical force or affinity is at the same time more intimate 
and more powerful. It modifies the molecules themselves. It 
brings heterogeneous substances into intimate relations, and 
thus produces new molecules. A consideration of the examples 
already cited may indicate more clearly the meaning of this 
important proposition. 

We have brought together sulphur and iron, and by their 
reciprocal action and the aid of heat there has been formed a 
new body, — sulphide of iron. We know that the smallest mass 
of sulphur we can obtain is composed of a collection of per- 
fectly homogeneous molecules, aggregated by cohesion. In each 



INTRODUCTION. 



23 



of them but one kind of matter can be found. It is the same 
with iron : the particles of this metal are perfectly homoge- 
neous. Sulphur and iron are simple bodies or elements. 

Let us now consider the sulphide of iron which results from 
their combination. This body also is formed of a collection of 
molecules, bound together by cohesion and perfectly similar to 
each other, but not homogeneous, for in each molecule we dis- 
tinguish two kinds of matter, — sulphur and iron. 

It cannot be admitted that these two substances are con- 
founded in the molecule, or that the effect of the combination 
of sulphur with iron is an interpenetration of the two bodies 
so intimate that they both disappear in what might be called a 
homogeneous mixture. On the contrary, it is supposed that 
the combination results from the juxtaposition of two infinitely 
small masses, each of which possesses a real magnitude and a 
constant weight. 

These little masses that no force, chemical or physical, can 
divide further, constitute the atoms. In each molecule of sul- 
phide of iron there exist two of these masses, — one of sulphur 
and one of iron ; and the atom of sulphur and the atom of 
iron are united, but not merged together, by chemical force. 
And when sulphur combines with iron it is because the atoms 
of the sulphur arrange themselves in juxtaposition with those 
of the iron, and it is affinity which brings about the action. 

When these atoms again separate, the sulphide of iron is said 
to decompose. When it attracts the atoms of another body, it 
is said to combine with that body. 

If sulphide of iron remain for some time exposed to moist 
air, its surface becomes covered with an efflorescence formed of 
a saline matter. In this case it has attracted one of the ele- 
ments of the air, oxygen, with which it has combined to form 
green vitriol or sulphate of iron. 

As we shall see later on, we have reason to believe that the 
molecules of oxygen gas are each formed of two atoms, but 
these atoms are of the same kind ; the molecules of sulphide 
of iron, on the contrary, are each formed of two unlike atoms, 
— one of sulphur and one of iron. These attract four atoms 
of oxygen, which constitute two molecules of that gas, which 
group themselves around the atom of sulphur and the atom 
of iron, forming with them one single molecule, more complex 
than the original molecule of sulphide of iron, for it contains 
in addition four atoms of oxygen. 



24 



ELEMENTS OF MODERN CHEMISTRY. 



1 molecule 
sulphide of iron. 



1 molecule 
oxygen. 



1 molecule 
oxygen. 









and there results 



1 molecule 
sulphate of iron. 

0-©-0 
©-©-0 - 

It is seen from wliat precedes that the words molecule and 
atom are far from being synonyms. The chemical molecule 
constitutes a whole of which the atoms form the parts, and 
these atoms are held together by affinity. In the preceding 
figure, this exchange of affinities between the atoms is indi- 
cated by lines of union. 

Chemical molecules have been well compared to edifices : 
the atoms constitute the materials, and it is readily conceived 
that such molecular edifices diff'er from each other according 
to the nature, number, and arrangement of the atoms, that is, 
the materials composing them. 

An edifice may be enlarged by the addition of new parts : it 
may be reduced in size or it may be entirely demolished. In 
the same manner a chemical molecule may be increased by the 
annexation of new atoms, or diminished by the separation of 
some of those which it already contains. In the first case 
there is combination, in the second, decomposition. 

We may still further consider these phenomena of combina- 
tion and decomposition. 

Since the combination of two bodies results from the recip- 
rocal action of their atoms, and has for efiect a change in the 
nature of the molecules, it is evident that it can only take 
place when these atoms, and consequently the molecules, are 
brought into intimate relations ; or more precisely, when the 
molecules of one of the bodies enter within the sphere of 
action of the molecules of the other body. And this sphere 
of action is very limited, for the affinity or elective attraction 
of the atoms is only exercised at infinitely small distances. 



INTRODUCTION. 25 

In consequence affinity is often retarded by cohesion, wHcli 
maintains the relations between the molecules of a solid body. 
These two forces are frequently in opposition, and that the 
first may attain the supremacy it is necessary that the other 
shall yield. To make manifest or to increase the affinity be- 
tween two bodies, it is then necessary to diminish their cohe- 
sion. On this condition the molecules can enter within the 
spheres of their reciprocal attraction, and the atoms of one 
body can attract those of the other. 

It has been seen from one of the experiments already cited 
that in order to combine iron with sulphur it is necessary to 
elevate the temperature. Now, the heat, by fusing the sul- 
phur, diminishes its cohesion, and, giving its molecules freedom 
of motion, puts them into more intimate contact with those of 
the iron. Chemical action then commences. 

Instead of heating the sulphur and iron to bring about 
chemical action, it would be sufficient to moisten the mixture 
with water. By the intervention of this liquid the particles 
of sulphur and of iron are, as it were, cemented together and 
thus brought into more intimate relations. For a stronger 
reason can chemical action between two solids be facilitated by 
dissolving them both in water and mixing the solutions. Dis- 
solved, they themselves assume the liquid state and lose, in 
great part, their cohesion. The ancients understood the in- 
fluence of the liquid state upon reactions, and stated it with 
exaggeration : Corpora non agwit nisi soluta. 

Although the liquid state facilitates chemical reactions, it 
does not follow that it always determines them. Frequendy 
liquids and even gases, after being mixed, must be heated 
before they will react upon each other. 

Experiment. — In a glass tube (Fig. 3) two gases, oxygen 
and hydrogen, are mixed in the proportion of one volume of 
the first to two of the second. Although the mixture is per- 
fectly homogeneous and very intimate, and although the cohe- 
sion of the gaseous molecules is null, no action takes place- 
But as soon as the mixture is heated by approaching a lighted 
taper to the mouth of the tube, combination takes place ener- 
getically. An explosion occurs and the two gases unite, form- 
ing water. In this case the heat has determined combination 
by increasing the intensity of the movements which animate 
the molecules of each gas, and so bringing the molecules of the 
one within the sphere of attraction of those of the other. 
B 3 



26 



ELEMENTS OF MODERN CHEMISTRY. 



The electric spark produces the same effect, and it probably 
acts by the heat which it communicates to the mixture. 




Fig. 3. 



More rarely combination is brought about by the influence 
of light. 

If a small bottle be filled with a mixture of equal volumes 
of hydrogen and chlorine gases, and then thrown into the air 
so that it may be struck by the direct rays of the sun, the 
combination of the two gases takes place instantly and with 
explosion. 

Such are some of the conditions which favor or determine 
chemical combination. Let us now study the circumstances 
which accompany these phenomena. 

Experiment. — If sulphur be strongly heated in a small glass 
flask until it begins to boil, and some copper turnings be then 
thrown into the flask, a brilliant incandescence takes place im- 
mediately. It is produced by the combination of the two 
bodies. Charcoal, sulphur, and phosphorus produce a brilliant 
light when they are burned in oxygen. Their combination 
with the gas takes place with evolution of light and heat. 

When any combustible body whatsoever is burned in the 
air, the heat and light are developed by the combination of the 
body with oxygen, one of the elements of the air. In general, 
all chemical combinations give rise to the production of heat, 
more or less intense ; in many cases it is accompanied by 
light ; sometimes it is scarcely perceptible. 

While heat acts as the determining cause of a great number 



INTRODUCTION. 



27 



of combinations, and while it is the result of such combination, 
it may play still another role in chemical reactions. In place 
of favoring combination, it may act in the opposite manner, 
separating atoms which are united by chemical attraction. 

Mercury retains indefinitely its brilliant surface when ex- 
posed to the air at ordinary temperatures, but at a temperature 
near its boiling-point it slowly attracts the oxygen of the air, 
and becomes covered with an orange-red powder, which is oxide 
of mercury. In this case heat has assisted the formation of a 
compound. 

If, however, this red powder be heated in a small retort to a 
temperature near redness, it is again resolved into mercury, 
which appears in drops in the neck of the retort, and into 
oxygen which may be collected. 

In this case an intense heat breaks up the compound which 
is formed at a temperature less elevated ; it occasions a decom- 
position. 

Heat acts thus in a great number of cases. A body is said 
to decompose when the elements composing it are separated 
from each other. 

The electric spark may occasion such separation when it is 
passed through compound gases. If a series of electric dis- 
charges be passed through ammonia gas, the latter is decom- 
posed., that is, resolved into its two elements, — nitrogen and 
hydrogen. 

In like manner, the current of the voltaic pile decomposes 
a great number of chemical compounds, the elements of which 
separate and appear, each at its appropriate pole of the bat- 
tery. The decomposing action exerted by the electric cur- 
rent upon chemical compounds was discovered about the com- 
mencement of the present century by Nicholson and Carlisle. 
These physicists were the first to decompose water by this 
agent. 

Lastly, light may decompose certain bodies, among which 
are a great number of the compounds of silver. The art of 
photography is founded upon the decomposing action of light 
upon certain of these combinations. 

There is another class of decompositions which it is impor- 
tant to consider with attention. They are occasioned by the 
intervention of more powerful affinities than those which 
maintain united the elements of a compound body. 

If copper be heated in the air, it attracts oxygen and is con- 



28 



ELEMENTS OF MODERN CHEMISTRY. 



verted into a black powder, a compound of oxygen and copper, 
wliicli is called oxide of copper. The affinity which unites the 
two bodies is considerable ; it cannot be overcome by the ac- 
tion of heat alone ; at any ordinary temperature to which the 
oxide so formed may be exposed, the atoms of copper still re- 
main intimately associated with those of the oxygen. But if 
this oxide be mixed with powdered charcoal and then heated, 
a moment arrives when the affinity of the charcoal for the oxy- 
gen is superior to that of the copper. The atoms of oxygen 
then abandon the copper and combine with the charcoal, thus 
forming a new compound, carbonic acid, which is disengaged 
in the form of gas. Here there is at the same time decompo- 
sition and combination. The molecules of oxide of copper are 
decomposed ; those of carbonic acid are formed. 

Nothing is created in combinations ; nothing is lost in de- 
compositions. In the preceding experiment only copper re- 
mains ; the charcoal and oxygen have disappeared, but their 
substance is not lost. All of the matter of the charcoal is 




Fig. 4. 



found combined with all of the matter of the oxygen in the 
product of their combination, the carbonic acid, in such a 
manner that the weight of the latter added to the weight of 
the copper remaining, exactly represents the weight of the 
oxide of copper and charcoal 



INTRODUCTION. 29 

Experiment. — Some oxide of mercury, of which we have 
seen the decomposition by heat, may be placed in a tube 
through which is passed a current of hydrochloric acid gas, a 
gas composed of chlorine and hydrogen (Fig. 4). An ener- 
getic reaction takes place. The orange-red powder is converted 
into a white crystalline substance, and much heat is produced. 
At the same time a small quantity of liquid condenses in the 
bulb. This is water, and the white powder formed is mercuric 
chloride, or corrosive sublimate, a compound of mercury and 
chlorine. The hydrochloric acid has converted the mercuric 
oxide into mercuric chloride. The mercury, at first combined 
with oxygen, is now combined with chlorine. But what has 
become of the oxygen ? It has combined with the hydrogen 
of the hydrochloric acid, forming water. We have brought 
into presence of each other two compound bodies : 

Mercuric oxide, 
Hydrochloric acid, 

and from their reciprocal action two new compounds result : 

Mercuric chloride, 

Water or oxide of hydrogen. 

This reaction has then occasioned an interchange of elements. 
The mercury of the mercuric oxide has combined with the 
chlorine of the hydrochloric acid, and the oxygen has left the 
mercury and combined with the hydrogen, which was aban- 
doned by the chlorine. The reaction has been as easy as 
energetic, thanks to the intervention of two affinities, for the 
affinity of chlorine for mercury has been aided by that of hy- 
drogen for oxygen. Two molecules are decomposed, and two 
new molecules are formed by an exchange which may be rep- 
resented in the following manner : 

BEFORE THE REACTION. 

Mercury + Oxygen = Mercuric oxide. 
Hydrogen + Chlorine = Hydrochloric acid. 

DURING THE REACTION. 




AFTER THE REACTION. 

Mercury -^ Chlorine = Mercuric chloride. 
Hydrogen + Oxygen = Water. 



30 ELEMENTS OF MODERN CHEMISTRY. 

Such reactions, characterized by an interchange of elements, 
are called douhle decompositions. They are the more usual 
reactions in chemistry. 

The examples cited have been demonstrated by experiments 
easy to comprehend and to repeat, and are sufficient to give an 
idea of chemical phenomena. We have seen how, on the con- 
tact of two heterogeneous bodies, this elective attraction, which 
is called affinity and which sets in motion the smallest particles 
of bodies, comes into play to produce either combination or 
decomposition ; we have seen how this force modifies the 
chemical molecules either by interposing other molecules, or 
under the influence of physical forces, such as heat and elec- 
tricity. The study of all these phenomena constitutes chem- 
istry, the science of molecular changes ; a science grand in 
purpose and in magnitude, since it penetrates to the very 
nature of the bodies surrounding us ; a science unlimited in 
its applications, since through it we learn to know and control 
the powerful forces which are at work in the most intimate 
structure of matter. 

If we trace the acquired facts to the most obvious and most 
certain conclusion, we must admit the existence of a number 
of bodies, each of which, when submitted to the various tests 
consisting in the application of physical and chemical forces, 
furnishes but one and the same substance, and it is impossible 
to obtain anything else than this substance from the body. We 
maintain, then, until proved to the contrary, that each of these 
bodies contains but a single kind of matter, to which the name 
simple body or element is applied. The chemical forces reside, 
as has been seen, in the most remote particles, in the atoms of 
these bodies. In uniting together, the elements form compound 
bodies, and it has already been stated that such combinations 
result from the juxtaposition of the atoms which attract each 
other. The idea of atoms was originally an hypothesis, but in 
its development it has been found to be supported by so many 
important facts, and moreover to weave them together in the 
most natural manner, that it has attained the dignity of a 
theory. Chemists have universally adopted it, and it has ren- 
dered immense service to the science. Let us proceed, now, 
to a consideration of the facts upon which it is based. 



LAW OF DEFINITE PROPORTIONS. 



31 



LAW OF DEFINITE PROPORTIONS. 




Fig. 5. 



The proportions by weight according to which bodies combine are invari- 
able for each combination — These proportions are equivalent among 
themselves — Experiments demonstrating this fact. 

Experiment. — A test-glass (Fig. 5) contains a liquid which 
is universally known as sulphuric acid. Although largely di- 
luted with water, that is, 
mixed with a large quan- 
tity of that liquid, it still 
manifests its presence by 
energetic properties. It 
has a very sour and cor- 
rosive taste, — a quality of 
an acid. If a few drops 
of blue litmus solution be 
added to it the blue color 
instantly changes to bright 
red. Another glass contains 
a solution of caustic potash 
or potassium hydrate. This 
substance possesses a strong, lye-like, alkaline taste, very easy 
to distinguish from that of the acid. The color of the blue 
litmus is not affected by this liquid, but if a few drops of the 
litmus solution, previously reddened by an acid, be added, the 
blue color is immediately restored. This caustic substance 
has properties which are different from those of acids, and 
which are called basic or alkaline properties. Potassium 
hydrate is an alkali or powerful base. 

If now the alkaline liquid, which has a blue color, be poured 
drop by drop into the reddened acid, and the mixture be 
stirred with a glass rod, a moment arrives when the red color 
of the acid liquid changes to blue. Exactly at this moment 
we have a solution which has no action upon litmus ; it will 
not redden the blue solution, neither will it restore the blue 
color to the red. This may be demonstrated by dipping into 
it first a red and then a blue litmus-paper. Furthermore, this 
liquid possesses neither the acid taste of the oil of vitriol nor 
the alkaline taste of the caustic potash, but its taste is salty. 

By their mixture and reciprocal action the sulphuric acid 
and the potash have lost the energetic properties which they 



32 ELEMENTS OF MODERN CHEMISTRY. 

manifested before mixing. Thej are exactly saturated ; they 
are neutralized. That is, the liquid which now contains both, 
or more properly the product of their reaction, is neither acid 
nor alkaline ; it is neutral, and its neutrality is manifested 
both by its indifference to vegetable colors and by its taste. 
There is no excess, neither of sulphuric acid nor of potash, 
but the two bodies have reacted exactly upon each other and 
both have disappeared, and from their reciprocal action two 
new bodies result, — a salt called potassium sulphate, and 
water. 

Whenever sulphuric acid is thus saturated by potash, there 
arrives a moment when the ^whole of the acid is precisely neu- 
tralized by the alkali, and when the two bodies are converted, 
without residue of either one or the other, into potassium sul- 
phate and water ; and it is always easy to recognize the instant 
at which this effect is produced by the action of the liquid upon 
vegetable colors, such as solution of litmus, or syrup of violets. 
The latter is reddened by an acid, changed to green by an 
alkali, and assumes its natural violet tint when the neutral 
point is reached. Now, it has been found that this last effect 
IS only produced when the acid and the alkali are mixed in 
certain proportions, which remain invariable, whatever may be 
the quantities which are mixed. In other words, it has been 
found that the quantities of sulphuric acid and potash which 
reciprocally neutralize each other and form potassium sulphate, 
maintain a constant ratio to each other. It may be easily proved 
that when the state of neutrality has been once attained, it is 
immediately passed and disturbed by the least excess of either 
acid or base that may be added to the liquid. This is made 
evident by the immediate change in the color of the liquid to 
either red or green. 

Thus, in order to form sulphate of potassium with a given 
quantity of sulphuric acid, it is necessary to add an invariable 
quantity of potash ; and if the quantity of sulphuric acid be 
increased by a third, or in any proportion whatever, it is neces- 
sary to increase by a third, or in the same proportion, the quan- 
tity of potash. 

Experiments of this kind have been made with other acids 
and other bases, and have introduced into the science the fun- 
damental notion that these bodies react upon each other in 
definite proportions to form salts, and that consequently the 
composition of the latter bodies is perfectly fixed. A given 



DEFINITE PROPORTIONS. 33 

quantity of any acid whatever, invariably saturates a. fixed 
quantity of the same base. This, then, is the first point. 

It may be added that similar researches made towards the 
close of the last century have led to a not less important result, 
namely, the respective quantities of several acids which satu- 
rate a given weight of one base are exactly proportional to the 
quantities of the same acids which saturate a given weight of 
another base. The law which governs the composition of salts 
was discovered towards the close of the last century by a G-er- 
man chemist, Richter. We cannot now expose it in detail ; 
such development will be better placed and better understood 
in that part of this work which treats of the formation of salts. 
For the present it is sufficient to state that the law mentioned 
is a consequence of the law of definite proportions, and that 
the latter law is universal. It applies not only to the reaction 
of acids upon bases, but is true for all chemical combinations. 
It is generally known as Dalton's first law, and may be thus 
expressed : the relative weights according to which bodies com- 
bine are invariable for each combination. 

There is one feature of the laws which control the composi- 
tion by weight of bodies that it is important to comprehend well. 

It may be best illustrated by experiment : 

100 gr. of mercury are put into the presence of chlorine 
gas, a body possessing very powerful affinities. In this man- 
ner mercuric chloride or corrosive sublimate is formed, and it 
is found that 35.5 gr. of chlorine are necessary to convert 100 
gr. of mercury into this compound. These figures — 100 and 
35.5 — express the invariable ratio in which these elements are 
combined in corrosive sublimate. Here we have the definite 
proportions. 

Now let the 135.5 gr. of corrosive sublimate be dissolved in 
water, and a plate of copper be placed in the solution ; this 
metal will displace the mercury, and combining with the 35.5 
gr. of chlorine will form with it cupric chloride, which will 
remain in solution, coloring the liquid green. The 100 gr. of 
mercury are then precipitated, and it will be found that 31.75 
gr. of copper have entered the solution and actually combined 
with 35.5 gr. of chlorine. 

Into this solution of cupric chloride a plate of zinc is now 
plunged ; all of the copper is precipitated in its turn, and 33 
gr. of zinc enter into combination with the 35.5 gr. of chlorine, 
forming zinc chloride. 



I 



34 ELEMENTS OF MODERN CHEMISTRY. 

The 35.5 gr. of chlorine lia^fe now been combined success- 
ively with 

100 gr. of mercury, 

31.75 gr. of copper, i 

33 gr. of zinc. 

These numbers, which express the respective quantities of 
mercury, copper, and zinc which combine with the same quan- 
tity of chlorine, may be called the equivalents of these metals. 
In fact, these quantities are equivalent to each other in relation 
to the same quantity of chlorine, the experiment having shown 
us that in order to displace 100 gr. of mercury combined with 
35.5 gr. of chlorine it is necessary to employ 31.75 gr. of 
copper or 33 gr. of zinc. 

To continue, 100 gr. of mercury are combined with oxygen, 
and it is found that this quantity of the metal requires 8 gr. of 
oxygen to form the red powder called mercuric oxide. 

But how much oxygen is necessary to form cupric oxide 
with 31. V5 gr. of copper? Kemarkable as it seems, exactly 
8 gr. are required, and 8 gr. are also requisite to form oxide 
of zinc with 33 gr. of zinc. 

100 gr. of mercury, 
31.75 gr. of copper, 
33 gr. of zinc, 

which are equivalent compared to 35.5 gr. of chlorine, are then 
also equivalent in relation to 8 gr. of oxygen. 

Chlorine itself may be oxidized, and there exists a gaseous 
compound of chlorine and oxygen which contains precisely 8 
gr. of oxygen for 35.5 gr. of chlorine. 

Thus, there are required 

35.5 gr. of chlorine to form chlorides with. . ill^^^fg^. oTZZlll 
8 gr. of oxygen to oxidize { 33 gr. of zinc, 

and also 

8 gr. of oxygen to oxidize 35.5 gr. of chlorine. 

In general, if 

A, B, C, combine with D, 

A, B, C, combine also with E, 

and further, D combines with E, 

the letters A, B, C, D, E, representing the weights of the dif- 
ferent elements which enter into combination, or the propor- 
tions according to which the bodies combine among themselves. 



MULTIPLE PROPORTIONS. 



35 



They are expressed by numbers tbat have been called combin- 
ing weights or equivalents ; these represent the ratio of weights 
or the relative weights. They are indeed relative to a unit 
which has served as a term of comparison, and which is the 
equivalent of hydrogen. That is, the quantity of hydrogen 
which combines with 35.5 of chlorine being 1, the equivalent 
quantities of oxygen, zinc, copper, and mercury will be repre- 
sented by the numbers 8—33—31.75—100. 

These are the facts of experiment. Let 33 gr. of zinc be 
treated with hydrochloric acid, the latter is immediately de- 
composed ; its chlorine combines with the zinc, forming chlo- 
ride of zinc, and its hydrogen is disengaged. In this experi- 
ment the hydrogen of the hydrochloric acid is simply displaced 
by the zinc. Now, 33 gr. of this metal will displace exactly 
1 gr. of hydrogen. 

It is seen that the numbers which have been given do not 
express absolute quantities, but merely the relative weights ac- 
cording to which the bodies combine or replace each other in 
compounds, these relative weights being compared to that of 
hydrogen, which is taken as unity. 



f which represent 
J equivalent quan- 
I titles of these 
I elements. 



Such is the signification of the numbers. 

100 31.75 33 35.5 8 1 

of of of of of of 

mercury, copper, zinc, chlorine, oxygen, hydrogen, 

This being admitted, in order to determine the equivalent 
of an element it is sufficient to find the quantity of that ele- 
ment which combines either with 1 of hydrogen or with a 
quantity of another element which is equivalent to 1 of hydro- 
gen, for instance, 8 of oxygen. 

The notion of equivalent proportions can be understood from 
the preceding considerations ; it appears as a consequence of 
the law of definite proportions ; it comprehends certain facts 
relative to the laws of the composition of bodies, but it by no 
means represents the full scope of these laws. The following 
developments add important features. 



MULTIPLE PROPORTIONS. 



Two bodies may combine in several proportions. Thus, 
with oxygen, carbon forms two compounds, both of which are 
gaseous. The less rich in oxygen is carbon monoxide ; the 
richer is carbon dioxide, or carbonic acid gas. Dalton was the 



36 ELEMENTS OP MODERN CHEMISTRY. 

first to perceive that for the sarae quantity of carbon, carbonic 
acid contains exactly twice as much oxygen as carbon monoxide. 
He made analogous observations concerning the composition 
of two compounds of carbon and hydrogen, the monocarbide 
of hydrogen or marsh gas, and the dicarbide of hydrogen or 
olefiant gas. From these observations he deduced the law of 
multiple proportions, which may be thus stated : when two 
bodies^ simple or compound^ unite in several proportions to 
form several compounds, the iveight of one of these todies 
being considered as constant, the weights of the other vary 
according to a simple ratio. 

Thus, taking up one of the examples given above, carbon 
unites with oxygen in two proportions : 

Carbon monoxide contains 16 parts of oxygen to 12 parts 
of carbon. 

Carbon dioxide contains 32 parts of oxygen to 12 parts of 
carbon. The numbers 16 and 32 are in the ratio of 1 : 2. 

Nitrogen forms five compounds with oxygen ; if such quan- 
tities of these compounds be taken as contain the same weight 
of nitrogen, the weights of the oxygen will be proportional 
to the numbers 1, 2, 3, 4, 5. 

Nitrogen monoxide contains for 28 parts of nitrogen 16 parts of oxygen. 
Nitrogen dioxide " 28 '' " 32 " " 

Nitrogen trioxide " 28 " " 48 " " 

Nitrogen tetroxide " 28 " " 64 " " 

Nitrogen pentoxide " 28 " " 80 " " 

These numbers, 16, 32, 48, 64, 80, are multiples of the first 
by the numbers 1, 2, 3, 4, 5. 

Five compounds of manganese and oxygen are known, and 
similar relations exist between the quantities of oxygen con- 
tained in these compounds. 

The first contains 55 parts of manganese to 16 of oxygen. 
The second " 55 " " 24 " 

The third " 65 « " 32 " 

The fourth « 65 " " 48 « 

The fifth « 55 " " 66 

The numbers 16, 24, 32, 48, 56 are in the simple propor- 
tion 1 : 1.5 : 2 : 3 : 3.5. 

Such is the law of multiple proportions discovered by 
Dalton. 

HYPOTHESIS OF ATOMS. 

The brilliant researches of Dalton did not terminate with 
the acquisition of facts : he sought to account for them by a 



GAY-LUSSAC'S LAWS. — ATOMIC THEORY. 37 

theoretical conception. Taking up the old idea of Leucippus 
and the word of Epicurus, he supposed all ponderable matter 
to be composed of indivisible particles which he called atoms. 
He gave a precise meaning to the vague and ancient notion by 
considering on one hand that the atoms of each kind of matter, 
of each element, possess an invariable weight, and on the other 
that combination between different kinds of matter results from 
the juxtaposition of their atoms. Such is the atomic hypothe- 
sis, the substance of which we have already indicated in treat- 
ing of chemical phenomena in a general manner. It permits 
a simple and rational interpretation of the laws of the compo- 
sition of bodies, and establishes between these laws a firm bond 
of theory. 

Indeed, if the combination of bodies results from the juxta- 
position of their atoms, the latter being considered as indivisi- 
ble and possessing a constant weight for each element, it is 
evident that combination can only take place in definite pro- 
portions, for these proportions represent the invariable relations 
between the weights of the atoms which are in juxtaposition. 
If, on the other hand, one body may combine with another in 
several proportions, such combination can only take place by 
the juxtaposition of 1, 2, 3, 4, etc., atoms of one body with 
one or more atoms of the other. It evidently results that the 
weight of the latter body being constant, the weights of the 
other in these various combinations must be multiples of each 
other. 

An hypothesis which gives such a simple and precise ex- 
planation of the facts relative to definite and multiple propor- 
tions is surely worthy of attention. It acquires still further 
import and becomes elevated to the rank of a theory when to 
these facts are added others entirely different from the first, 
but not less important. 

GAY-LUSSAC'S LAWS.— ATOMIC THEORY. 

Gases combine in simple volumetric proportions — Relations which exist 
between the volumes of gases and their atomic and molecular weights — 
Equal volumes of gases or vapors contain the same number of molecules 
— The molecular weights are equal to double the densities compared to 
hydrogen. 

Among these new facts it is convenient to first notice those 
which were discovered by Gray-Lussac, from 1805 to 1808. 
They relate to the volumes of gases which combine together. 



38 



ELEMENTS OF MODERN CHEMISTRY. 



Experiment.— A straight graduated glass tube about one metre 
long, closed at one end and having two platinum wires soldered 
through the glass near the closed end, is filled with mercury and 
inverted over a tall glass mercury cistern (Fig. 6), in the bottom 
ot which is a thick caoutchouc pad. This tube, which is called a 
eudiometer, is surrounded by a wider glass tube fitting firmly on a 
cork passed over the eudiometer. The cork is also perforated for the 
passage of a bent glass tube through which steam from a boiler can 
be delivered into the space between the eudiometer-tube and the 
mantle. The mouth of the eudiometer being about one centimetre 




Fig. 6. 



below the level of the mercury, which completely fills the cistern, 
a mixture of two volumes of hydrogen with one volume of oxygen 
is now introduced until the level of the mercury in the tube indi- 
cates the latter to contain exactly 30 cubic centimetres. The wires 
of the eudiometer are now connected with the poles of an induction- 
coil, and steam is passed from the boiler until it no longer condenses 
in the space between the tubes ; that is, when the temperature is 
100°. The gases have been expanded by the heat, and the eudiometer 
must be lowered into the cistern until the level of the mercury in 
the tube again marks 30 cubic centimetres, when the clamps of the 



GAY-LUSSAC'S LAWS. — ATOMIC THEORY. 39 

stand are so adjusted that tlie upper one is fixed at this mercury 
level. The tube is now lowered into the mercury until its lower 
end rests upon the caoutchouc pad ; a spark from the coil is passed 
in the eudiometer, and this causes the oxygen and hydrogen to com- 
bine instantly, as is seen by a bright flash. Now, on raising the 
tube until the mercury in it stands as before, at the level of the 
upper clamp, it is found that the eudiometer contains only 20 cubic 
centimetres of gas instead of 30. The 20 cubic centimetres consist 
of steam formed by the union of 20 cubic centimetres of hydrogen 
with 10 cubic centimetres of oxygen. As the apparatus cools, the 
steam will condense to water, and as the latter occupies a very small 
volume compared with that of the steam, the mercury will rise and 
fill the tube. 

Prom the facts thus established we draw the conclusion that 2 
volumes of hydrogen exactly combine with 1 volume of oxygen to 
form 2 volumes of vapor of water. 

There is thus determined a simple ratio not only between the vol- 
umes of hydrogen and oxygen which combine, but further, between 
the volume of vapor of water formed and the sum of the volumes 
of the composing gases. 3 volumes of the latter are reduced to 
exactly 2 by the combination. 

Analogous facts have been discovered for other gases, as shown 
by the following examples : 

2 volumes of nitrogen + 1 volume of oxygen = 2 volumes of nitrogen monoxide. 
2 volumes of chlorine -f 1 volume of oxygen = 2 volumes of chlorine monoxide. 

In other cases the combination of two gases determines a still 
greater contraction, and the initial volume is reduced one-half. Thus 

1 volume of nitrogen + 3 volumes of hydrogen — 2 volumes of ammonia gas. 

Finally, when two gases combine in equal volumes, their combi- 
nation usually takes place without contraction; in other words, the 
volume of the gas produced is equal to the sum of the volumes of 
the component gases. 

From these collected facts we may draw tlie following general 
conclusions : 

1. There is a simple relation between the volumes of gases 
which combine. 

2. There is a simple relation between the sum of the volumes 
of the combining gases and the volume of the gas resulting 
from the combination. 

These laws were first signalized by Gay-Lussac, whose name 
is attached to them. Their importance is immense ; they have 
added a. notable development to the atomic theory. 

If the definite proportions by weight in which bodies com- 
bine represent, according to Dalton, the relative weights of 
their atoms, it is natural to conclude that the definite and 
simple proportions by volume in which gases combine , accord- 



40 



ELEMENTS OF MODERN CHEMISTRY. 



ing to Gray-Lussac, represent the volumes occupied by the 
atoms. Under the same volume gases would then contain 
the same number of atoms. This was first proposed by Am- 
pere, who based his conclusion on the important consideration 
that gases dilate and contract nearly equally when submitted 
to the same variations of temperature and pressure. Within 
certain Hmits the proposition is true ; it applies to a large num- 
ber of simple gases. But if equal volumes of these gases, 
measured, let it be well understood, under the same conditions 
of temperature and pressure, contain the same number of atoms, 
it is evident that the weights of these equal volumes should 
represent the weights of the atoms. In other words, the 
atomic weights of the simple gases should be proportional to 
their densities. 

The densities of gases and vapors represent the weights of 
these gases or vapors compared to the weight of an equal 
volume of air. To determine the density, a certain volume of 
the given gas is weighed, and this weight is divided by that of 
an equal volume of air, under the same conditions of tempera- 
ture and pressure. The air is then the unit to which are com- 
pared the densities of gaseous bodies. On comparing these 
densities to that of hydrogen,^ which we take as unity, we find 
that the same numbers express almost exactly the densities and 
the atomic weights, the unit to which the densities are com- 
pared, that is, hydrogen, being the same as that to which are 
compared the atomic weights. The figures in the following 
table demonstrate this to be the case : 



Elements. 


Densities of 
Gases or Vapors, 
Air being Unity. 


Densities, 

Hydrogen being 

Unity. 


Atomic 
Weights. 


Hydrogen 

Oxygen 

Nitrogen 

Sulphur (density at 1000°) 

Chlorine 

Bromine 

Iodine 


0.0695 

1.1015 

0.9714 

2.22 

2.44 

5.53 

8.716 


1 

15.9 
14 
32 
35.2 
79.7 
125.8 


1 

15.9 
14 
32 
35.5 
80 
127 



1 To do this it is suflBcient to multiply the densities of the gases compared 

to air by = 14.388, which is the density of the air compared to hy- 

0.0695 - f -^ *- 

drogen as unity. 



GAY-LUSSAC'S LAWS. — ATOMIC THEORY. 41 

It is seen from this table that if the densities of gases be 
compared to hydrogen as unity, just as the weights of their 
atoms are compared to hydrogen as unity, the same figures, or 
very nearly the same figures, express both the densities and 
the atomic weights. We may add that, for all the elements 
taken in the gaseous state, there has been determined between 
the densities referred to hydrogen and the atomic weights, if 
not equality, at least a simple ratio. These remarkable rela- 
tions were pointed out by Gay-Lussac. 

Equal volumes of the simple gases above enumerated con- 
tain the same number of atoms. Two volumes of hydrogen, 
then, contain twice as many atoms as one volume of oxygen ; 
and when these gases combine in the ratio of 2 volumes of the 
first to 1 of the second, we must admit that each atom of oxy- 
gen combines with 2 atoms of hydrogen. We say, then, that 
water is composed of 2 atoms of hydrogen and 1 atom of oxy- 
gen. These three atoms so united constitute the smallest 
quantity of water that can exist in the free state. This is 
called a molecule of water. 

But what volume does this molecule occupy ? The experi- 
ment has shown us. We have seen that 2 volumes of hydro- 
gen, in combining with 1 volume of oxygen, yield 2 volumes 
of vapor of water. One molecule of water in the gaseous state, 
then, occupies 2 volumes, if 1 atom of hydrogen occupy 1 
volume, and if 1 atom of oxygen occupy 1 volume. It is 
seen that the volumes represent the atoms, and the relative 
weights of equal volumes, that is, the densities, represent the 
weights of the atoms. 

Let us now consider another compound gas, — ammonia, — 
composed of hydrogen and nitrogen. A very simple experi- 
ment will show in what proportion the atoms of these elements 
are combined in this gas, and the volume occupied by the 
compound compared with the volumes of its component gases. 

Experiment. — 100 volumes of ammonia gas are introduced 
into a tube inverted upon the mercury-trough (Fig. 7), and 
the walls of which are pierced at the upper end by two plati- 
num wires, between the ends of which a small space is left. 
To these wires are attached the extremities of the two con- 
ducting wires of a RuhmkoriF coil, and the current is passed 
so that a series of electric sparks traverses the ammonia between 
the extremities of the wires in the tube. The gas is imme- 
diately decomposed, and the level of the mercury in the tube 

4* 



42 



ELEMENTS OF MODERN CHEMISTRY. 



is depressed. When the experiment has terminated it is found 
that the vohime of the gas has been doubled. Instead of 100 
volumes, there are now 200, the gas being measured under the 
same conditions of temperature and pressure as before. It is 
found, by an analytical process that will be indicated further 
on, that these 200 volumes of gas resulting from the decompo- 




FiG. 7. 

sition of 100 volumes of ammonia are composed of 150 vol- 
umes of hydrogen and 50 volumes of nitrogen. These 150 
volumes of hydrogen and 50 volumes of nitrogen are condensed 
by their union into 100 volumes of ammonia. In other words, 
3 volumes of hydrogen and 1 volume of nitrogen are combined 
together in 2 volumes of ammonia. And as the volumes rep- 
resent atoms, it follows that in ammonia gas 3 atoms of hydro- 
gen are combined with 1 atom of nitrogen. But the quantity of 
ammonia containing 1 atom of nitrogen and 3 atoms of hydro- 
gen is the smallest quantity of ammonia that can exist. It is 
a molecule of ammonia, and this molecule occupies 2 volumes, 
if 1 atom of nitrogen or 1 atom of hydrogen occupy 1 volume. 

Here, then, is another compound gas, — ammonia, — of which 
the molecule occupies 2 volumes, like that of water. It is the 
same with all the gases. All of the atoms which are combined 
to constitute the molecule of a gas or vapor are so condensed 
that the molecule occupies the same volume as the molecule of 
hydrogen, of vapor of water, or of ammonia. 

We may state, then, with the Italian chemist, Avogadro, 
that equal volumes of gases contain the same number of mole- 
cules^ and that each of these molecules occupies 2 volumes, if 
1 atom of hydrogen occupy 1 volume. It follows that the 
weight of 2 volumes of any gas, whether elementary or com- 
pound, represents the weight of its molecule, the weight of 



GAY-LUSSAC'S LAWS.— ATOMIC THEORY. 43 

one volume of hydrogen being 1. But the weight of 2 vol- 
umes of a gas or vapor is twice its density compared to hy- 
drogen, for the density is the weight of 1 volume compared 
with the weight of 1 volume of hydrogen. To find the weight 
of the molecule (the weight of 2 volumes) of a gas or vapor, 
it is then only necessary to multiply its density compared to 
hydrogen (the weight of 1 volume) by 2. 

The densities of gases and vapors are generally referred to 
air as unity. To bring them to the hydrogen standard, they 
are multiplied by the number expressing the relation of the 
density of hydrogen to that of air, which is -Q.-^^-g-g- = 14.388. 
The product thus obtained expresses the density compared 
to hydrogen, that is, the weight of 1 volume. To find the 
weight of 2 volumes, or the molecular weight, it is then only 
necessary to multiply the densities compared to air by twice 
the ratio of the density of the air compared to hydrogen, 
that is, by the constant factor, — 

_l 2_ _ 

^ ^ 0.0695 — 0.0695 " 28.776. 

It is seen that if the atomic weights of certain gases can be 
deduced from a comparison of their densities, this same physi- 
cal notion may also serve for the determination of the molecu- 
lar weights of compound gases. 

The numbers which represent double the densities of gases 
or vapors compared to hydrogen, express also the molecular 
weights of these gases or vapors, that is, the sum of the 
weights of all the atoms in the molecule, the weight of one 
atom of hydrogen being 1. 

Considering the examples already given, we may deduce the 
molecular weights of water and of ammonia from the densities 
of steam and ammonia gas. 

The density of vapor of water, determined by Gray-Lussac 
is 0.6235. To find the molecular weight of water, it is suffi- 
cient to multiply this figure by 28.776. The product, 17.9, 
expresses the weight of a molecule of water, which is indeed 
composed of 

2 atoms of hydrogen =2 

1 atom of oxygen = 15.9 

1 molecule of water z= 17.9 

Sir Humphry Davy found for the density of ammonia the 



44 ELEMENTS OP MODERN CHEMISTRY. 

number 0.5901. This being multiplied by 28.776, the prod- 
uct, 16.98, should represent the weight of one molecule of 
ammonia. Ammonia contains 

3 atoms of hydrogen 3 

1 atom of nitrogen ........ 14 

1 molecule of ammonia 17 

The discovery of the laws which govern the combination of 
gases by volume has seconded in the most efficacious manner 
the progress of the atomic theory. 

In the first place, it has established a marked distinction be- 
tween the old idea of equivalents and the modern one of atoms. 
The equivalents represented merely the ponderable proportions 
according to which bodies combine ; the atomic weights repre- 
sent the relative weights of the volumes of gases which com- 
bine. The equivalent of hydrogen — unity — expressed merely 
that hydrogen was the unit to which were referred the weights 
of other bodies with which it entered into combination. The 
atomic weight of hydrogen is the weight of one volume of 
hydrogen, taken as unity, and to this unit are referred the 
atomic weights of other bodies. 

In the second place, the discovery of Gay-Lussac has shown 
how the atomic weights of simple bodies and the molecular 
weights of compound bodies can be deduced from the densi- 
ties of gases and vapors. 

However, this resource would be insufficient in very many 
cases. It only applies to gaseous bodies, or such as can be con- 
verted into vapor without decomposition. Now, there are many 
substances with which this is impossible, and serious difficul- 
ties would be encountered in the determination of the atomic 
weights of certain elements were it not for another physical 
law, discovered by two French physicists, Dulong and Petit. 
It denotes the relations which exist between the specific heats 
and the atomic weights. 

LAW OF SPECIFIC HEATS. 

It is known that in order to raise the temperatures of differ- 
ent bodies through the same number of thermometric degrees 
very different amounts of heat are required. Thus, one kilo- 
gramme of water requires 30 times more heat than one kilo- 
gramme of mercury to raise its temperature one degree, and 
if the quantity of heat required to raise the temperature of 



LAW OF SPECIFIC HEATS. 



45 



one kilogramme of water one degree be represented by 1, tbe 
quantity required to raise the same weight of mercury one 
degree will be represented by 0.0333 = ■^. This fraction ex- 
presses the specific heat of mercury between and 100°. 

The specific heat of a solid or liquid body is then the amount 
of heat required to raise the temperature of a certain weight of 
the body one degree, the amount required to raise the tempera- 
ture of an equal weight of water one degree being taken as 
unity. 

In 1820, Dulong and Petit discovered the remarkable fact 
that if the figures which express the atomic weights of the 
elements, liquid or solid, be multiplied by those which express 
their specific heats, the product obtained is sensibly constant ; 
in other words, the specific heats of the elements are inversely 
as their atomic weights. It follows that if such quantities of 
the elements be taken as represent their atomic weights, the 
amount of heat required to raise the temperature of each one 
degree will be sensibly the same. The law discovered by Du- 
long and Petit may then be expressed, — the atoms of the solid 
elements possess sensibly the same specific heats. 

This law permits the deduction of the atomic weights from 
the specific heats. Indeed, it is evident that if the product of 
the specific heats by the atomic weights be a constant, that 
may be called the atomic heat.^ dividing this product by the 
specific heat should give the atomic weight. The product 
which represents the atomic heat is approximately 6.4, as may 
be seen from the followinoj table : 



Names of the Solid Elements. 


Specific 
Heats. 


Atomic 
Weights. 


Products of the 
Specific Heats 
by the Atomic 

Weights. 
Atomic Heats. 


Sulphur, between and 100° . . 
Selenium 


0.2026 
0.0762 


32 

79.5 
127 

80 
127 

31 

75 

12 

n 

28 
39.1 


6.483 

6.058 

6.023 

6.744 

6.873 

5.850 

6.105 

5.52 

5.5 

5.66 

6.500 




0.0474 


Bromine, between — 78 and — 20° 
Iodine, between and 100° . . 
Phosphorus, between -\- 1 and 30° 
Arsenic 


0.0843 
0.0541 
0.1887 
0814 


Carbon, diamond, at 600° . . . 
Boron, crystallized, at 600° . . 
Silicon, at 1000° 


0.46 

0.5 

0.202 




0.1695 







46 



ELEMENTS OF MODERN CHEMISTRY. 

TABL^.— Continued. 



Names of the Solid Elements. 



Sodium, between — 34 and + 7° . 

Lithium 

Thallium' 

Magnesium 

Aluminium 

Manganese 

Iron 

Zinc 

Cadmium 

Cobalt 

Nickel 

Tungsten 

Molybdenum 

Lead 

Bismuth 

Copper 

Antimony 

Tin 

Mercury, between — 77.5 and — 44° 

Silver 

Gold .......... 

Platinum 

Palladium 

Osmium 

Rhodium 

Iridium 



Specific 
Heats. 



0.2934 

0.9408 

0.03355 

0.2499 

0.2143 

0.1217 

0.0110 

0.09555 

0.05669 

0.1068 

0.1089 

0.0334 

0.0722 

0.0314 

0.0308 

0.09515 

0.06077 

0.05623 

0.03247 

0.05701 

0.0324 

0.03293 

0.0693 

0.031 

0.05803 

0.03259 





Products of the 


Atomic 


Specific Heats 


'Woi crVi ta 


by the Atomic 




Weights. 




Atomic Heats. 


23 


6.748 


7 


> 6.586 


204 


6.844 


24 


5.998 


27 


5.786 


65 


6.693 


56 


6.116 


66.2 


6.230 


112 


6.349 


59 


6.301 


69 


6.424 


184 


6.146 


96 


6.931 


207 


6.499 


210 


6.468 


63.5 


6.042 


120 


6.092 


118 


6.635 


200 


6.494 


108 


6.167 


197 


6.383 


195 


6.421 


106.5 


6.316 


191 


5.921 


104.4 


6.058 


193 


6.291 



Carbon, silicon, and boron have long been regarded as ex- 
ceptions to Dulong and Petit's law. Their specific heats had 
been determined at comparatively low temperatures, and the 
products of the numbers obtained by the atomic weights fell 
much below 6.4. These exceptions have disappeared ; the ex- 
periments of Weber have shown that the specific heats of 
carbon, silicon, and boron increase with the temperature, and 
that for the first two elements they attain limits, where they 
remain sensibly constant. The figures given in the preceding 
table for these three elements are those of Weber, and it is 
seen that on multiplying them by the respective atomic weights 
of carbon, silicon, and boron, values are obtained which ap- 
proximate 6.4. 

It will otherwise be remarked that there are sensible differ- 



ISOMORPHISM. — CHEMICAL NOMENCLATURE, ETC. 47 

ences between the numbers expressing tli« atomic beats of tbe 
various solid elements, showing that Dulong and Petit's law, 
although true in its generality and striking in its enunciation, 
is not free from certain perturbations which give to it the 
character of an approximate law. It is the same with other 
physical laws, Mariotte's law, for example. 

ISOMORPHISM. 

While considering the atomic theory and the determination 
of the relative weights of the ultimate particles of bodies, we 
cannot pass in silence a discovery which has had a great influ- 
ence upon the development of that theory. It is due to E. 
Mitscherlich, who, in 1819, made known the law of isomor- 
phism. This law may be thus stated : there is such a relation 
between the atomic constitutions of compound bodies belonging 
to the same group and their crystalline form, that " the same 
number of atoms combined in the same manner produce the 
same crystalline form, the latter being independent of the 
chemical nature of the atoms, and determined solely by 
their number and arrangement." While this proposition is 
not strictly true, it has rendered important aid in the study of 
atomic structure of bodies. We will reconsider it when treating 
of the general characteristics of salts, but we may remark here 
that it has been of great value in the determination of certain 
atomic weights. Indeed, in some cases considerations of a 
chemical nature cannot decide between two numbers for the 
atomic weight of a given element. The choice is then deter- 
mined by the following considerations : such a value must be 
attributed to the atomic weight that the isomorphous com- 
pounds formed by the element, and by another to which it is 
analogous, may be represented by similar atomic formula. 

The methods employed for the determination of the molec- 
ular weights of such bodies as cannot be vaporized without de- 
composition will be described under " Organic Chemistry" (page 
442). 

CHEMICAL NOMENCLATURE AND NOTATION. 

General Considerations. — Nearly eighty substances are 
known which have not been resolved into simpler forms of 
matter, and are consequently considered as simple bodies or 
elements. By combining together, they form an innumerable 
multitude of com,pound bodies containing two or more elements. 



48 ELEMENTS OF MODERN CHEMISTRY. 

In order to distinguisli these bodies from each other it is neceS' 
sary to give a name to each, for each constitutes a distinct sub- 
stance. 

The names of the simple bodies have been chosen at will, 
and in some cases recall some peculiar property of the sub- 
stances designated. It was formerly the same with compound 
bodies ; there was no definite rule for their nomenclature. 
From this there resulted a great complication of words which 
erabarrassed the exposition of ideas, and often for the same sub- 
stance there were a number of synonyms, of which the least 
inconvenience was to uselessly fatigue the memory. Hence 
chemists have felt the necessity of a regular nomenclature, 
applicable to compound bodies, and capable of indicating their 
composition. Such is the principle of the chemical nomen- 
clature suggested by Guyton de Morveau, and developed by 
Lavoisier, Berthollet, and Fourcroy. This nomenclature, with 
some modifications, introduced by the progress of the science, 
is still adopted. 

Independently of this language, the rules of which will 
presently be detailed, chemists have adopted a written nota- 
tion which expresses in concise form the atomic constitution 
of compounds. The name of each element is represented by 
a symbol, which also expresses one atom of the substance. 
This symbol is the initial letter of the name of the element, 
or the initial letter with another when the names of two ele- 
ments begin with the same letter. Thus, H represents one 
atom of hydrogen weighing 1 ; represents one atom of 
oxygen weighing 16. By combining these symbols together, 
it is easy to represent in a precise manner the atomic compo- 
sition of compound bodies. From such combinations result 
chemical formulas, the use of which was introduced into the 
science by Berzelius. 

In the following table will be seen the names of the ele- 
ments now known, together with their atomic weights, and the 
symbols by which the atoms of the elements are represented in 
the notation. 

The greater number of the elements possess certain physi- 
cal properties which characterize them as metals. They are 
opaque, and possess a peculiar lustre, which does not disappear 
under the burnisher. They are good conductors of heat and 
electricity. 

Other elements, fewer in number, do not possess these prop- 



CHEMICAL NOMENCLATURE AND NOTATION. 



49 



Names of the Ele- 
ments. 



Aluminium . . . 

Antimony (stibium] 

Argon . 

Arsenic 

Barium 

Bismuth 

Boron . 

Bromine 

Cadmium 

Ca3sium 

Calcium 

Carbon 

Cerium 

Chlorine . 

Chromium 

Cobalt . 

Copper 

Erbium 

Fluorine 

Gadolinium . 

Gallium . . 

Germanium . . 

Glucinum (beryl 

Hum) . . 
Gold (aurum) 
Helium . . 
Hydrogen 
Indium . . 
Iodine . . . 
Iridium . . 
Iron (ferrum) 
Krypton . . 
Lanthanum . 
Lead (plumbum 
Lithium . . 
Magnesium . 
Manganese . 
Mercury (hyd 

gyrum) 
Metargon 
Molybdenum 



m 


o » 






5 


i-a 


1- 


^l 


Al 


26.9 


Sb 


119.5 


A 


40(?) 


As 


74.46 


Ba 


136.4 


Bi 


206.5 


B 


10.9 


Br 


79.34 


Cd 


111.55 


Cs 


131.9 


Ca 


39.8 


C 


11.9 


Ce 


138.0 


CI 


35.18 


Cr 


51.7 


Co 


51.7 


Cu 


63.1 


Er 


164.7 


F 


18.9 


Gd 


156 (?) 


Ga 


69.5 


Ge 


71.9 


Gl 


9.01 


Au 


195.7 


He 


4(?) 


H 


1 


In 


113.1 


I 


125.89 


Ir 


191.7 


Fe 


55.6 


Kr 


80(?) 


La 


137.6 


Pb 


205.36 


Li 


6.97 


Mg 


24.1 


Mn 


54.6 


Hg 


198.5 


A^t 


40(?) 


Mo 


95.3 



Names of the Ele- 
ments. 



Neodymium . . . 

Neon 

Nickel 

Niobium (colum- 

bium) 

Nitrogen , . . . 

Osmium 

Oxygen 

Palladium . . . . 
Phosphorus . . . 
Platinum . . . . 
Potassium (kalium) 
Praseodymium . . 

Radium 

Rhodium . . . . 
Rubidium . . . . 
Ruthenium . . . 
Samarium . . . . 
Scandium . . . . 

Selenium 

Silicon 

Silver (argentum) . 
Sodium (natrium) . 
Strontium . . . . 

Sulphur 

Tantalum .... 
Tellurium .... 

Thallium 

Thorium 

Thulium 

Tin (stannum) . . 
Titanium .... 
Tungsten (wolfra- 

mium) 

Uranium 

Vanadium .... 

Xenon 

Ytterbium .... 

Yttrium 

Zinc 

Zirconium .... 



Nd 

Ne 
Ni 
Nb 

N 

Os 



Pd 

P 

Pt 

K 

Pr 

Ra 

Rh 

Rb 

Ru 

Sa 

Sc 

Se 

Si 

Ag 

Na 

Sr 

S 

Ta 

Te 

Tl 

Th 

Tu 

Sn 

Ti 

W 

U 

V 

X 

Yb 

Y 

Zn 

Zr 



2*2 



142.5 
22(?) 
58.25 
93.03 

13.93 
189.6 

15.88 
106.2 

30.76 
193.4 

38.82 
139.4 

(?) 
102.2 
84.75 
100.9 
149.2 
43.8 
78.6 
28.2 
107.11 
22.88 
86.95 
31.83 
181.5 
126.5 
202.61 
230.8 
169.4 
118.1 
47.8 

182.6 
237.8 

51 
128 (?) 
171.9 

88.3 

64.9 

90.6 



erties. They are known as the non-metals, or metalloids, and 
include 



ARGON. 


CHLORINE. 


IODINE. 


NITROGEN. 


SILICON. 


ARSENIC. 


FLUORINE. 


KRYPTON. 


OXYGEN. 


SULPHUR. 


BORON. 


HELIUM. 


METARGON. 


PHOSPHORUS. 


TELLURIUM 


BROMINE. 


HYDROGEN. 


NEON. 


SELENIUM. 


XENON. 


CARBON. 










C d 




5 







50 



ELEMENTS OF MODERN CHEMISTRY. 



It is impossible, however, to separate the metals from the 
non-metals by an exact line of demarcation. 

Nomenclature of Compound Bodies. — The principle of 
chemical nomenclature is to indicate the composition of com- 
pound bodies by their names. Among such compounds the 
most numerous and the most important are those containing 
oxygen. They are binary or ternary ; that is, the oxygen in 
them is combined with one or two other elements. 

Binary Oxygen Compounds. — We will first consider the 
more simple oxidized bodies, those which result from the com- 
bination of oxygen with but one other element, metallic or 
non-metallic. These compounds are called oxides, and diifer 
as the element associated with the oxygen is metallic or non- 
metallic. In combining with non-metallic elements, oxygen 
generally forms compounds which are the anhydrides of acids, 
that is, compounds capable of uniting with water to form 
acids ; with the metals it forms metallic oxides. 

Experiments. — 1. A small piece of phosphorus is placed in 
a capsule floating on the surface of mercury. It is ignited 
and the capsule covered with a bell-jar (Fig. 8). The phos- 
phorus burns, giving off a thick smoke, which condenses in 




white flakes on the sides of the bell-jar. This substance re- 
sults from the combination of the phosphorus with the oxygen 
of the air : it is phosphorus pentoxide^ oi phosphoric anhydride. 



CHEMICAL NOMENCLATURE AND NOTATION. 51 

2. If lead be heated in the air and maintained for some 
time in a state of fusion, its brilliant surface becomes tarnished 
and covered with grayish particles, which are finally converted 
into a yellow powder. This body is formed by the combina- 
tion of the lead with oxygen : it is plumbic oxide, or oxide of 
lead. 

But, as we have seen, such combination can take place in 
different proportions. An atom of a body may unite with 
1, 2, 3, or more atoms of oxygen, and the names of the com- 
pounds so formed should indicate the degree of oxidation. 

Sulphur forms two compounds with oxygen : one contains 2 
atoms of oxygen to 1 atom of sulphur ; the other, 3 atoms of 
oxygen to 1 of sulphur. They are designated by the names 
sulpliuro?<s oxide, or anhydride, and sulphuric oxide, or anhy- 
dride. 

The written notation represents them by the symbols 

so^ 

so^ 

which express their atomic compositions. The number of 
atoms of any element is indicated by a small figure placed after 
and a little above or below the symbol of that element. 

The degree of oxidation is then expressed by the termina- 
tion in ous or ic of the name of the other element, which 
indicates the kind of oxide, ic denoting the superior oxide. 

Mercury forms two compounds with oxygen. The first 
contains 2 atoms of mercury for 1 of oxygen ; the second, 1 
atom of mercury to 1 of oxygen. They are designated by the 
names and symbols as follows : 

Mercurous oxide Hg^O 

Mercuric oxide HgO 

The names monoxide, sesquioxide, dioxide, etc., as will be 
seen further on, are also employed.^ 

A monoxide is a combination of 1 atom of metal with 1 atom of oxygen. 
A sesquioxide " " 2 atoms '' " .3 atoms " 

A dioxide " " 1 atom " " 2 " " 

It is easy then to understand the signification of the follow- 
ing names and symbols : 

1 The prefixes proto, hi or dent, and ter have been, and are yet, frequently 
employed instead of mono, di, and tri. 



52 ELEMENTS OE MODERN CHEMISTRY. 

Manganese monoxide MnO 

Manganese sesquioxide Mn^O^ 

Manganese dioxide MnO^ 

The oxide most rich in oxygen is sometimes called the per- 
oxide. 

Oxygen Acids and Metallic Hydroxides. — The oxygen 
compounds that we have just considered may unite with the ele- 
ments of water to form more complex compounds, which are 
ternary,' that is, they contain three elements. To the two ele- 
ments of the oxide is then added a third, independently of the 
oxygen of the water, that is, its hydrogen. 

The oxygen acids usually result from the union of water 
with the non-metallic oxides. 

Experiment. — Sulphur trioxide or sulphuric anhydride 
occurs in white silky tufts. It is very volatile, and if a bottle 
containing it be opened, its vapor comes in contact with the 
moist air and forms thick white fumes. If a small quantity of 
this substance be thrown into water, it immediately disappears 
and combines with that liquid. So great is the energy of the 
reaction that the heat disengaged gives rise to the production 
of steam, which, being suddenly formed and condensed in the 
midst of the cooler liquid mass, causes a peculiar noise, a sort of 
hissing. When the sulphuric oxide is dissolved in the water, 
the solution presents a very acid reaction. It contains sulphuric 
acid, the compound long known under the name of oil of vitriol. 

This reaction may be represented in the abbreviated lan- 
guage of the notation, which expresses the atomic composition 
of bodies with so much precision. The formula of sulphuric 
anhydride or sulphur trioxide is 

SO^ 
that of water is 

Then if sulphuric acid result from the addition of all of the 
elements of water to those of sulphuric trioxide, it should contain 

SO-^ + H^O = H'^SO* 

This is a chemical equation^ and it is seen that the two 
terms of the first member express the atomic composition of 
the reacting bodies, while the single term of the second mem- 
ber gives the atomic composition of the product of the reac- 
tion. Such an equation accounts for all of the atoms, and 



CHEMICAL NOMENCLATURE AND NOTATION. 53 

the sum of all of the atoms written in the first member must 
exactly balance the sum of all those written in the second. 

There is a compound known as nitric anhydride, or nitrogen 
pentoxide. It results from the combination of nitrogen with 
oxygen, and its atomic composition is represented by the 
formula N^O^. In combining with water it forms nitric acid. 

N^O^ + H^O = 2(HNO0 

Nitric anhydride. Water. Nitric acid. 

(1 molecule.) (2 molecules.) 

These examples, which could be indefinitely multiplied, give 
an idea of the constitution of the ternary oxygen acids. The 
rules which have been already given for the nomenclature of 
the oxides apply also to the nomenclature of the acids. We 
have phosphorous acid and phosphoric acid. .S^po-phosphor- 
ous acid is an acid of phosphorus containing still less oxygea 
than phosphorous acid. {Hypo, literally, under.) 

The metallic hydrates or hydroxides result from the reaction 
of water with metallic oxides. It is known that when quick- 
lime is sprinkled with water it becomes heated, increases in 
volume, cracks into pieces, and is finally converted into a white, 
impalpable powder, which constitutes slaked lime, — a com- 
pound of the lime with water. Lime is the oxide of a metal 
called calcium. In combining with water it forms a ternary 
compound of calcium, hydrogen, and oxygen; this is calcium 
hydroxide, or, as it is commonly called, hydrate of lime. 

CaO + H^O = CaH^O^ 

Calcium oxide. Water. Calcium hydroxide. 

(Lime.) 

The metal potassium, the radical of potash, forms with oxy- 
gen a compound which contains two atoms of potassium com- 
bined with one atom of oxygen. The composition of this body 
is then represented by the formula K^O. 

It combines with water with great energy, and forms with it 
potassium hydroxide, or caustic potash, 

K^O + H^'O = 2K0H 

Potassium oxide. Water. Potassium hydroxide. 
(2 molecules.) 

Oxygen Salts. — The oxygen salts result from the action of 
the oxygen acids upon the metallic oxides or hydroxides. 

Experiment. — The formation of a salt may be illustrated by 
a modification of one of the experiments already described. 

A quantity of dilute nitric acid is slightly reddened by a so- 
5* 



54 ELEMENTS OF MODERN CHEMISTRY. 

lution of blue litmus or syrup of violets.^ Some dilute solution 
of caustic potash is also treated with the same coloring matter ; 
the syrup of violets will assume a green color, or blue litmus 
will remain unchanged. 

The latter liquid, which is alkaline, is now added drop by 
drop to the acid, until the red color disappears, giving place to 
the violet color of the syrup of violets or the blue of the litmus. 
The liquid is now neutral. It contains neither free nitric acid 
nor free potash. Both have disappeared as such ; they are 
reciprocally neutralized, the first having lost its acid taste, the 
second its extreme caustic properties. They have produced a 
body having a saline, cooling taste, and exerting no action upon 
vegetable colors. It is a neutral salt which has been formed. 
It is called potassium nitrate, and is the nitre or saltpetre of 
the ancient chemists. It is not, however, the sole product of 
the reaction. Water is formed at the same time, and if we 
would comprehend the entire phenomenon, the reaction will be 
expressed by the following equation : 

HNO^ + KOH = KNO^ + H^O 

Nitric acid. Potassium hydroxide. Potassium nitrate. Water. 

It is seen that the salt, potassium nitrate, is a ternary com- 
pound, similar in constitution to nitric acid itself. On com- 
paring the two formulae, 

HNO^ nitric acid, 
KNO'^ potassium nitrate, 

it is seen that they only differ by the K in the second occupy- 
ing the place held by the H in the first. It may then be said 
that potassium nitrate represents in a manner nitric acid in 
which the hydrogen has been replaced by an equivalent quan- 
tity of potassium. This definition applies to the entire class 
of compounds under consideration. A salt represents an acid 
of which the hydrogen has been wholly or partially replaced 
by an equivalent quantity of metal. 

The acids constitute the salts of hydrogen : they are neu- 
tralized when this hydrogen is replaced b}^ a metal. The acid 
or hydrogen salt diifers from the metallic salt. From a theoretic 
point of view, an acid is a compound of the same order as a 
salt, and if these bodies are separated by such great differences 

1 An infusion of common purple cabbage may be substituted for syrup 
of violets. 



CHEMICAL NOMENCLATURE AND NOTATION. 55 

of properties, this is due to the nature of the base. What 
a difference, indeed, between hydrogen gas and the metals ! _ 

We have studied the formation of a salt by the action of an 
acid, nitric acid, upon a metallic hydroxide, potassium hydroxide. 
The anhydrous oxides may also form salts by reacting with acids. 

Experiment. — Yellow oxide of lead, wb^n digested with 
dilute sulphuric acid, is converted into a white, insoluble pow- 
der, which is lead sulphate. This is a salt, but it is not the only 
product of the reaction, for water is formed at the same time. 
H^SO^ + PbO = PbSO* + H^O 

Sulphuric acid. Lead oxide. Lead sulphate. Water, 

Lastly, among other modes of formation of salts, there is one 
which is worthy of interest, and of which an idea may be ob- 
tained from the following example. 

Sulphur trioxide, or sulphuric anhydride, combines energetic- 
ally with barium oxide or baryta, and from the union of all of 
the elements of both compounds there results a salt, — barium 
sulphate. 

SO^ + BaO = BaO,SO^ or BaSO* 

Sulphur trioxide. Barium oxide. Barium sulphate. 

But, whether this salt be formed under these conditions, or 
by the action of sulphuric acid, its composition only differs 
from that of the latter acid by the substitution of Ba for H^. 
H^SO* sulphuric acid, hydrogen sulphate, 
BaSO* barium sulphate. 

The reactions which we have just studied, and which indicate 
the principal methods of the formation of salts, are sufficient to 
make clear the definition before given, that salts are derived from 
acids by the substitution of a metal for hydrogen. The nomen- 
clature defines and preserves these relations. To distinguish the 
different salts of the same acid, the name of the metal is placed 
first, and this is followed by the name of the acid, which is but 
slightly changed, — ic is changed to ate^ and ous to ite. 

Thus Sulphuric acid gives sulphates. 

Nitric acid " nitrates. 

Perchloric acid " perchlorates. 

Sulphurous acid " sulphites. 

Hyposulphurous acid " hyposulphites. 

These generic names follow the names of the metals which 
enter into the composition of the salts, and which specify them, 
as it were, Thus, we have ; 



56 ELEMENTS OF MODERN CHEMISTRY. 

Potassium sulphate, copper sulphate, lead sulphate, etc. ; 

Sodium sulphite ; 

Potassium nitrate, barium nitrate, silver nitrate, etc. 

But we know that a single metal may form several com- 
pounds with oxygen. In reacting upon the same acid these 
diiFerent oxides give rise to the formation of different salts. 

Thus, two different sulphates of mercury are obtained, as 
sulphuric acid is caused to react with mercurous oxide, or with 
mercuric oxide. 

H^SO* + Hg^O = Hg^SO* + H^O 

Sulphuric acid. Mercurous oxide. Mercurous sulpbate. Water. 

H^SO* + HgO = HgSO^ + H^O 

Mercuric oxide. Mercuric sulphate. 

It is easy to distinguish these two salts from each other by 
using the adjectives mercurous and mercuric before the sub- 
stantive sulphate. Thus, we have chromows and chromic sul- 
phates ; ferrows and ferric sulphates. 

The preceding considerations will give an idea, sufficient for 
the time being, of the constitution and the nomenclature of 
salts. Their further exposition will be completed farther on. 

Nomenclature of Non-Oxygenized Compounds. — The non- 
metallic elements other than oxygen can combine among them- 
selves or with the metals. Such compounds are designated by 
the name of one of the elements followed by the abbreviated 
name of the other terminating in ide. Thus, the compounds 
of the metals with chlorine, bromine, iodine, sulphur, arsenic, 
and carbon are called chlorides, hromides, iodides, sulphi<ies, 
BiYsemdes, ca^vhides. We thus have sodium chloride, potassium 
bromide, lead iodide, zinc arsenide, iron carbide. The termi- 
nation uret was formerly used in place of ide. 

But a non-metallic body, such as chlorine or sulphur, can, 
like oxygen, form several compounds with the same metal. In 
these compounds 1 atom of metal may be united with 1 or 2 
atoms of sulphur, or with 1, 3, or 5 atoms of chlorine, or again 
with 2 or 4 atoms of chlorine. Such atomic composition is 
expressed by the following names and symbols : 

Iron monosulphide FeS 

Iron c?{sulphide FeS^ 

Phosphorus ^rtchloride . POP 

Phosphorus pentachloride PCl^ 

Tin (bichloride SnCP 

Tin tetrachloride SnCI* 

Antimony <r/chloride SbCl^ 

Antimony pentachloride ,,..,"... SbCl^ 



CHEMICAL NOMENCLATURE AND NOTATION. 57 

The names thus express precisely the number of atoms of 
the second element in combination with 1 atom of the first. 

The compounds of chlorine, bromine, iodine, and several 
other elements with hydrogen are acids ; they readily exchange 
their hydrogen for a metal, so forming compounds that are 
analogous to the oxygen salts, and which constitute the haloid 
salts of Berzelius. 

Experiment. — The compound of chlorine with hydrogen is 
hydrochloric acid ; it is a gas, and dissolves in water, forming 
a fuming, strongly-acid liquid. When it is carefully poured 
into a concentrated solution of caustic potash there appears a 
white precipitate, formed of little crystals and presenting the 
appearance of a salt. This is potassium chloride. It is formed 
according to the following reaction, and its formation is at- 
tended by the production of heat : 

HCl + KOH = KCl + H^O^ 

Hydrochloric Potassium Potassium Water.' 

acid. hydroxide. chloride. 

The hydrogen compounds of bromine, iodine, fluorine, sul- 
phur, etc., possess analogous properties. They are called 

Hydrobromic acid HBr 

Hydriodic acid HI 

Hydrofluoric acid HF 

Hydrosulphuric acid or sulphuretted hydrogen . H^S 

The chlorides may combine among themselves. It is the 
same with the bromides, iodides, sulphides, etc. If a solution 
of potassium chloride be poured into a concentrated solution 
of platinic chloride, a yellow precipitate, constituting a com- 
pound of the two chlorides, is formed. It is the double chlo- 
ride of platinum and potassium, or potassium chloroplatinate. 

There exist, likewise, double sulphides formed by the union 
of two simple sulphides. Such compounds constitute what are 
called sulpho-salts. 

Alloys and Amalgams. — Alloys are compounds or mix- 
tures of the metals with each other. Amalgams are the alloys 
of mercury, that is, the compounds of this liquid metal with 
other metals. 



58 



ELEMENTS OF MODERN CHEMISTRY. 



HYDROGEN". 

Density compared to air 0.0695 

Atomic weight (1 volume taken as unity) H = 1. 

This body was discovered in 1766 by Cavendish. It is one 
of the elements of water, hence its name, given by Lavoisier. 
Experiments. — 1. Into a piece of lead pipe about 4 milli- 
metres bore, 25 milli- 
metres long, and ham- 
mered shut at one end 
small pieces of sodium 
are pressed until the 
tube is full. The little 
tube is then inserted 
under the mouth of 
a jar filled with water 
and inverted in a ves- 
sel of the same liquid 
(Fig. 9). Bubbles of 
gas at once begin to 
rise, and by the use 
of several little tubes 
charged with sodium 
the jar can be soon 
filled with the gas 
(Newth). This is hy- 
drogen, produced by 
the decomposition of 
the water ; the reaction is expressed in the following equation : 
2W0 -f Na^ = 2NaOH + H^ 

Water. Sodium. Sodium hydrate. Hydrogen. 

If the jar be now inverted and a lighted taper brought to 
the orifice, the gas will burn with a pale flame, A piece of 
red litmus-paper will be at once colored blue by the sodium 
hydrate or caustic soda dissolved in 'the water in the vessel. 

2. Hydrochloric acid is poured upon small pieces of zinc in 
a glass cylinder (Fig. 10). Rapid efi"ervescence takes place, 
and if a lighted taper be brought to the mouth of the jar, the 
hydrogen evolved takes fire. This hydrogen is produced by 
the decomposition of the hydrochloric acid by the zinc, which 
is converted into chloride. 

2HC1 -f Zn = ZnCP + W 

Hydrochloric acid. Zinc. Zinc chloride. Hydrogen. 




HYDROGEN. 



59 



Preparation. — A reaction analogous to the preceding is 
turned to advantage for the preparation of large quantities of 
hydrogen. Dilute sulphuric acid is decomposed by zinc. 

A two-necked bottle is about half filled with water, and 
granulated zinc, or sheet-zinc 
cut into small pieces, is intro- 
duced ; sulphuric acid is then 
added in small quantities by 
the aid of a funnel-tube which 
dips under the surface of the 
water (Fig 11). The reaction 
at once commences, and hydro- 
gen is disengaged. When the 
air at first contained in the 
bottle has been entirely ex- 
pelled, the gas may be collected 
in jars or bottles filled with 
water and inverted on the 
pneumatic trough. 

In this reaction the zinc 
disappears and dissolves in 
the liquid with evolution of 
heat, and it often happens, if 
the liquid be sufiiciently con- 
centrated, that colorless crys- 
tals of zinc sulphate are formed 
on cooling. This salt and 
hydrogen are the sole prod- 
ucts of the reaction of pure 
zinc upon sulphuric acid largely diluted with water. 

H^SO* + Zn ^ ZnSO* + H^ 

Sulphuric acid. Zinc. Zinc sulphate. Hydrogen. 

Hydrogen may also be obtained by dissolving metals, such 
as zinc or aluminium, in a strong aqueous solution of potas- 
sium or sodium hydroxide. 




Fig. 10. 



2K0H -f Zn 



= Zn^O'K^ + 

Potassium zinc oxide. 



H^ 



When hydrogen gas absolutely free from impurities is 
needed, it is best to prepare it by decomposing water acidu- 
lated with sulphuric acid by the electric current (see page 80). 



60 



ELEMENTS OE MODERN CHEMISTRY. 




Fig. 11. 



Physical Properties. — Hydrogen is a colorless gas, and 
when pure has neither taste nor odor. It is the lightest of all 
known bodies, its density compared to air being 0.0695 ; that 

is, if one volume of 
air weigh 1, one vol- 
ume of hydrogen, 
measured under the 
same conditions of 
temperature and 
pressure, weighs only 
0.0695. Hydrogen 
is then 14,388 times 
lighter than air. The 
weight of one litre 
of hydrogen at 0° 
and under the nor- 
^'"mal pressure is 
0.0899 gramme. In- 
stead of comparing 
the densities of gases and vapors to that of air it is preferable 
to compare them to that of hydrogen taken as unity (p. 40). 
Hydrogen passes with great facility through vegetable and 
animal membranes, and through porous substances that are im- 
pervious to water. It cannot be kept in a glass vessel that 
presents the least crack, for it would pass through much more 
readily than air. This property is expressed by saying that hy- 
drogen is very diffusible. 

According to Magnus, it is the only gas gifted with an ap- 
preciable conductivity for heat ; in this respect it is related to 
the metals. 

Hydrogen is very slightly soluble in water, its coefficient of 
solubility being .0215 at 0° and .0174 at 25° (Timofejew). 

Of all the known gases hydrogen is, with one exception, 
the most difficult to liquefy. In order that any gas may be 
converted into the liquid state it is necessary that its mole- 
cules be made to manifest a certain degree of cohesion, and 
for every gas there is a temperature above which this cannot 
take place. This is called the critical temperature, and the 
pressure required at this point to bring about liquefaction is 
known as the critical pressure. For hydrogen, according to 
Olszewski, these conditions are — 234° and 20 atmospheres. 
By subjecting the gas to these conditions, several experi- 



HYDROGEN. 61 

menters had observed an evanescent mist, supposed to be 
made up of minute droplets of the liquid. In the " dynamic 
state," i.e.^ as a coherent mass, and in considerable quanti- 
ties, it was quite recently obtained by Dewar. Liquid hydro- 
gen is described as colorless and mobile. Its boiling point is 
about — 250°, and its density rather less than 0.07. 

Among the physical properties of hydrogen may be men- 
tioned the remarkable faculty it possesses of passing through 
plates of iron or platinum at high temperatures (H. Sainte- 
Claire Deville and Troost). It is well known that it rapidly 
passes through thin sheets of caoutchouc. According to 
Graham, this property is related to that possessed by certain 
solid bodies, and particularly metals, such as iron, platinum, 
and palladium, of absorbing hydrogen gas. This chemist 
designated the phenomenon by the name, occhision of hydro- 
gen by the metals. Palladium especially is distinguished by 
the energy with which it absorbs hydrogen. It can condense 
in its pores nine hundred times its own volume of the gas. A 
palladium wire may be charged with hydrogen by arranging it in 
a voltameter so that it constitutes the negative pole of a small 
battery, the positive pole being a stout platinum wire. When 
the current passes, the hydrogen set at liberty at the negative 
pole (see page 81) is condensed in the palladium. This metal 
undergoes at the same time a remarkable change. Its volume 
augments and its density diminishes, but its metallic lustre 
remains, as do also, to a certain degree, its tenacity and con- 
ductivity for electricity ; besides this, it becomes magnetic. 
There is thus formed a sort of alloy of palladium and hydro- 
gen, containing about 20 volumes of palladium to 1 volume of 
hydrogen reduced to the solid state. The density of this solid 
hydrogen compared to that of water, according to the determi- 
nations of Troost and Hautefeuille, is 0.62. Graham insisted 
upon the metallic character of hydrogen thus alloyed with 
palladium, but i\\Q properties of liquid and solid hydrogen, 
as observed by Dewar, do not accord with this view. 

Chemical Properties.— Hydrogen is a combustible gas, and 
the product of its combustion is water. 

Experiments. — 1 . A lighted taper may be thrust into a rather 
wide tube filled with hydrogen (Fig. 14). The gas takes fire 
on contact with the flame, but the taper is extinguished in the 
atmosphere of hydrogen. It may be relighted by withdrawing 
it through the burning gas. The experiment shows at the 



62 



ELEMENTS OE MODERN CHEMISTRY. 



same time that hydrogen is inflammable and that it is incapa- 
ble of supporting combustion itself. 

2. A gas-bottle, A (Fig. 12), is arranged for the preparation 
of hydrogen, and water, zinc, and sulphuric acid are intro- 




FiG. 12. 

duced. The hydrogen evolved is made to traverse the tube 
CB, which is filled with fragments of chloride of calcium ; after 
having been dried by this substance, which is very avid of 

water, the gas escapes by the tube 
a, the end of which is drawn out 
to a point. The jet of gas is 
lighted, and burns with a pale 
flame. A bell-jar, D, is now 
held over the burning jet, and 
the sides of the glass soon be- 
come covered with dew, the 
drops of which unite and run 
down to the edge of the jar. This 
is water, and it is formed by the 
combustion of the hydrogen ; that 
is, by its combination with the 
oxygen of the air. 

3. A jet of hydrogen may be 
lighted by holding in it a tuft of 
asbestos which has been dipped 
in platinum black, that is, finely -divided platinum. The con- 
densation of the hydrogen in the pores of the finely-divided 
metal is so rapid that the platinum becomes heated to redness, 
and then ignites the gas. 




HYDROGEN. 



63 



4. A tube filled with hydrogen may be held in the vertical 
position, bottom upwards, without the gas escaping rapidly by 
the inferior opening. If the tube be inclined, the hydrogen 
overflows and escapes upwards through the air. It may then 
be received in a second tube held vertically above the first, 
which is inclined more and more (Fig. 13). The passage of 
the gas into the upper tube can be demonstrated by approach- 
ing to the latter a lighted taper, when the hydrogen will burn 
with a faint explosion. 

Before igniting or collecting hydrogen escaping from a gen- 
erator, it should always be ascertained that the whole of the air 
has been expelled, otherwise dangerous explosions may result. 

5. The explosions may take place with the production of a 
harmonious sound, if they are made to succeed each other 





Fig. 14. 



Fig. 15. 



rapidly and at regular intervals. These conditions are realized 
by burning a small jet of hydrogen in a somewhat large tube 
(Fig. 15). The flame is drawn away from the jet by the draft 
in the tube, but immediately recedes as the ascending hydro- 



64 



ELEMENTS OF MODERN CHEMISTRY. 



gen gas mixes with the air, at the same time producing a faint 
explosion, and the rapid succession of these explosions* produces 
a musical tone. 

The hydrogen condensed in palladium appears to have chem- 
ical properties more active than those of gaseous hydrogen 
(Graham). It combines in the dark and at ordinary tempera- 
tures with iodine and chlorine ; the direct union of ordinary 
hydrogen with iodine is impossible, and with chlorine it takes 
place at the common temperature only under the influence of 
light. Hydrogen will not support respiration, but it is not 
poisonous. 



OXYGEN. 

Density compared to air 1.1015 

Density compared to hydrogen 15.88 

Atomic weight = 15.88 

Oxygen was discovered about the year 1774, and inde- 
pendently, by Scheele and 
by Priestley. The latter 
obtained it by heating red 
precipitate or mercuric 

P^^^^^^%l),W^ ^^ Experiment. — A small 

quantity of mercuric oxide 
is heated in a hard glass 
test-tube (a. Fig. 16). 
Presently the tube becomes 
lined with a mirror of me- 
tallic mercury which soon 
separates into little drops, 
and if a wooden splint 
bearing a spark at the end 
be thrust into the mouth 
of the tube, it instantly 
bursts into flame, and burns 
with great brilliancy. This 
eff'ect is due to a gas which 
^^^ ^g is being disengaged, and 

which, to use the expres- 
sion of Lavoisier, is eminently fitted to support combustion. 
It is the gas to which that great chemist gave the name 
oxygen. It is produced by a very simple reaction. The mer- 




OXYGEN. 



65 



curie oxide has been decomposed by heat into mercury and 
oxygen. 

2HgO = 2Hg + O-^ 

Mercuric oxide. Mercury. Oxygen. 

In the same manner a little potassium chlorate is heated in 
a test-tube. The salt first melts, then an elFervescence takes 
place, and this is due to disengagement of oxygen, as is easily 
proved by applying the spark test. 

Preparation. — Large quantities of oxygen may be pre- 
pared by a process based upon this reaction. When potassium 
chlorate is heat- 
ed, it is con- 
verted into 
potassium chlo- 
ride, and gives 
up all of its 
oxygen. To 
facilitate this 
decomposition a 
small quantity 
of manganese 
dioxide is mixed 
with the chlo- 
rate. The part 
taken by the 
manganese di- rm. n. 

oxide in the reaction is not thoroughly understood ; it is probable 
that it is converted into an unstable higher oxide, continually 
formed and decomposed during the reaction. If the tempera- 
ture be sufficiently elevated, the decomposition of the chlorate 
is complete, and takes place according to the following equation : 
2KC10^ = 2KC1 + 30^ 

Potassium chlorate. Potassium chloride. Oxygen. 




The operation may be conducted in a glass retort, which 
should be about one-third filled with the mixture of chlorate 
and dioxide ; to the beak of the retort is adapted a delivery- 
tube, which dips under the surface of the water or mercury in 
the trough (Fig. 17). The retort is then heated by an alco- 
hol or gas lamp, and the chlorate melts and disengages its oxy- 
gen with effervescence. Towards the close of the operation, 
the heat is increased in order to decompose into potassium 
chloride and oxygen any potassium perchlorate that may have 
6 6* 



m 



ELEMENTS OF MODERN CHEMISTRY. 




been formed by tbe union of a portion of the evolved oxygen 
with some of the chlorate. 

To make larger quantities of oxygen for filling the gas- 
holders of laboratories, 
etc., a mixture of potas- 
sium chlorate and man- 
ganese dioxide is 
heated in a sheet-iron 
or copper retort (Fig. 
18). 

At a bright red heat 
manganese dioxide 
gives up a third of its 
oxygen and is con- 
verted into the red ox- 
EiG. 18. ide of manganese. 

3MnO' = Mn^O* + 0^ 

Manganese dioxide. Red oxide of manganese. Oxygen. 

Powdered potassium dichromate may be heated with twice its 

weight of concentrated sulphuric acid. Oxygen is disengaged. 

2K^Cr^0^ -f 8K^S0*= 2K'S0*, Cr^SOO' + 8H^0 + 80^ 

Potassium dichromate. Potassium and chromium sulphate. 

On the large scale oxygen is manufactured by a process 
devised by Brin. Air is forced into a specially prepared porous 
barium oxide, BaO, at a temperature below redness, and barium 
dioxide, BdO^ is formed. The stream of air is cut off and the 
barium oxide is heated to redness, the pressure in the apparatus 
being lowered by air-pumps. The oxygen absorbed is now 
disengaged, and the barium dioxide is converted into monoxide 
ready to absorb more oxygen.^ 

Physical Properties. — Oxygen is a colorless, odorless, taste- 
less gas ; it is a little heavier than the air. If one volume of 
hydrogen weighs 1, the same volume of oxygen, measured 
under the same conditions of temperature and pressure, weighs 
15.88. This is expressed by saying that the density of 
oxygen compared to that of hydrogen is 15.88. A litre 
of oxygen weighs 1.429 gr. at 0° and under the normal 
pressure. 



1 Oxygen is now sold compressed in strong steel bottles, from which it 
may be conveniently drawn as required for experiment. 



OXYGEN. 



67 



Oxygen, which was formerly regarded as a permanent gas, 
was liquefied by Cailletet, and also by Pictet, in 1877. Its 
critical temperature is — 118°, and the critical pressure 50 
atmospheres. The liquid has a bluish color, its specific 
gravity is 1.124, and it boils at — 183°. 

Oxygen is but slightly soluble in water. A litre of water 
dissolves 0.041 litre, or 41 cubic centimetres, at 0° ; 0.032 litre 
at 10° ; 0.028 litre at 20°. The fractions 0.041, 0.032, 0.028, 
represent the coefficients of solubility of oxygen in water at 
the temperatures of 0°, 10°, and 20°. 

Chemical Properties. — Oxygen combines directly with most 
of the other elements, and the union often takes place with 
such energy that there results a great evolution of light and 
heat ; it gives rise to the phenomenon of combustion. 

Experiments. — A cone of charcoal of which the point is red- 
hot is plunged into a globe filled with oxygen (Fig. 19), and 
immediately combustion takes place with great brilliancy. The 
oxygen combines with the carbon, forming a colorless gas, which 
is carbonic acid gas. 

In like manner, sulphur and phosphorus burn in oxygen, the 
first producing a colorless, irritating gas known as sulphurous 





Fig. 20. 

acid gas, the second emitting thick fumes, which condense in 
white flakes of phosphoric oxide. 

A watch-spring may be drawn out into a spiral, and a small 
piece of tinder attached to one end ; after igniting the tinder, 
the spiral is rapidly plunged into a bell-jar filled with oxygen, 
and resting upon a plate containing a layer of water (Fig. 20). 
The tinder burns energetically, and heats the end of the spiral 
to redness ; then the combustion of the iron itself commences, 
and goes on with extraordinary brilliancy, and a production of 



68 ELEMENTS OF MODERN CHEMISTRY. 

heat 80 intense that the oxide of iron formed melts and falls 
in incandescent drops, which fuse themselves into the sur- 
face of the plate, even after having traversed the layer of 
water. 

In the same manner, the combustion of the metal magnesium 
may be effected in oxygen ; it takes place with dazzling splen- 
dor, and gives rise to the production of a white powder, which 
is magnesia, or magnesium oxide. 

The preceding experiments are examples of rapid combus- 
tion. We have seen that solid substances, such as charcoal, 
iron, and magnesium, become incandescent in combining with 
oxygen : it is the phenomenon of fire. We have also seen that 
vapors, like those of sulphur and phosphorus, become lumi- 
nous in their combination with oxygen : this is the phenome- 
non of flame. 

But fire and flame are not necessary concomitants of the 
union of bodies with oxygen. It is true that such union is 
always accompanied by the production of heat ; but often this 
heat is not attended by light ; sometimes it is imperceptible 
to our senses. 

Thus iron, the combination of which with oxygen at a red 
heat gives rise to such a brilliant combustion, may unite with 
this gas at ordinary temperatures under the influence of 
moisture. There is thus formed ferric hydrate, which consti- 
tutes rust. 

This oxidation of the iron, which takes place slowly, pro- 
duces a feeble disengagement of heat, which is, however, imme- 
diately dissipated. Such phenomena of oxidation are designated 
by the name slow combustion. 

The term combustion would then be synonymous with oxi- 
dation did we not know, on the other hand, that all chemical 
combination gives rise to the production of heat. If copper 
be thrown into boiling sulphur, a vivid incandescence is pro- 
duced, due to the union of the two bodies. Likewise antimony 
and arsenic, when projected in fine powder into an atmosphere 
of chlorine, unite with the latter body, producing a brilliant 
combustion. It is seen that in these cases the _ production of 
light and heat indicates an energetic combination, but not an 
oxidation. 

Oxygen is one of the elements of the air ; it is the cause 
and the agent of all combustion, of all oxidation which takes 
place in our atmosphere ; and the oxygen fixes itself upon 



OXYGEN. 69 

burning bodies in such a manner that the product of the com- 
bustion contains all of the matter of the combustible body and 
all of the matter of the oxygen. This is one of the fundamental 
truths of chemistry, and for its discovery not less than a cen- 
tury and a half of work was required. The glory of the dis- 
covery belongs to Lavoisier. 

His researches on combustion revealed to him the true 
nature of the phenomena of respiration. The respiration of 
animals is a slow combustion ; it is the source of animal heat. 
It gives rise to the formation of carbonic acid gas and water, 
products of the complete oxidation through which must pass 
those organic matters in the economy which no longer serve the 
purposes of life, and all of which contain carbon and hydrogen. 

The production of carbonic acid gas by the act of respira- 
tion is easy to prove. It is only necessary to blow, by the aid 
of a tube, the air contained in the lungs through clear lime- 
water, which soon becomes milky from the formation of insolu- 
ble carbonate of lime. 

An annular jet of hydrogen through which a jet of oxygen 
is forced constitutes what is known as the oxyhydrogen blow- 
pipe, and is one of the most intense sources of heat known. 
Platinum melts before it like wax, and iron and other combus- 
tible metals burn brilliantly when introduced into its flame. 
The flame of the oxyhydrogen blowpipe gives but little light, 
but when it is projected upon a piece of lime, the latter becomes 
heated to dazzling incandescence, constituting the Drummond 
or calcium light. 

OZONE, OR OXYGEN PEROXIDE. 

The repeated discharges of a good electric machine develop 
a peculiar odor. This is due to the production of a body which 
was discovered by Schonbein in 1840, and which he named 
ozone (from oCw, I smell). 

Experiment. — Some potassium permanganate is mixed with 
barium dioxide in a mortar, the mixture transferred to a flask, 
and moistened with sulphuric acid. The characteristic odor of 
ozone immediately becomes perceptible, and a moistened paper, 
impregnated with potassium iodide and starch and held in the 
neck of the flask, immediately assumes a blue color.^ This eff"ect 
is caused by the ozone evolved. 

1 Such a paper is called ozonoscopic. It is colored blue by the combina- 



70 



ELEMENTS OF MODERN CHEMISTRY. 



This remarkable body is also formed under the following 
circumstances. 

1. By the passage of electric discharges through oxygen. It 
is sufficient to pass a series of electric sparks through oxygen 

contained in a tube above a solu- 
tion of iodide of potassium and 
starch, in order to produce the 
blue color caused by the ozone 
(Fig. 21). 

It has been noticed that the 
largest quantity of ozone is pro- 
duced when the passage of the 
electricity through oxygen is ef- 
fected, not by sparks, but by non- 
luminous or silent discharges 
(Andrews and Tait, von Babo). 
I)ry and pure oxygen can be con- 
verted into ozone in this manner. 
But this conversion only takes 
place partially, the ozone formed 
remaining mixed with a large 
excess of oxygen. A contraction 
takes place at the moment the 
oxygen is transformed into ozone. 
These experiments prove that 
ozone is condensed oxygen. 

An elegant and efficient apparatus for the ozonation of oxy- 
gen by electricity was devised by Berthelot and is shown in 
Fig. 22. c is a long, thin glass tube closed at the bottom, 
near which a bent tube, &, is soldered in, while a similar tube 
is joined to it near the top. d is a narrower and longer tube, 
closed at one end, which passes nearly to the bottom of c, into 
the mouth of which it is adapted by a bulb and ground joint. 
d is filled with dilute sulphuric acid, and the whole apparatus 
is placed in a jar of the same, as shown in the figure. By 




Fig. 21. 



tion of the starch with the iodine set at liberty by the ozone. According 
to Houzeau, it is preferable to use a delicate, wine-colored litmus-paper, 
one-half of which is impregnated with potassium iodide. Ozone will change 
the color of this half to blue, for, in decomposing the potassium iodide, it 
forms potassium hydrate, and this restores the blue color to the litmus. 
Under these conditions, the other half of the paper undergoes no change 
in color, while it would be colored red by acid vapors, or blue by ammonia. 



OZONE. 



71 



platinum wires the columns of sulphuric acid are made the 
poles of an iuduction coil, and oxygen is passed by one of the 
side tubes through the annular space in the apparatus. Under 
the influence of the obscure discharges the gas is rapidly 
ozonized. 

The proportion of ozone formed is in- 
creased when the oxygen is cooled. At 
— 23°, a mixture of oxygen and ozone, 
containing 17.6 per cent, of the latter, , 
may be obtained, under normal atmospheric 
pressures. (Hautefeuille and Chappuis.) 

2. By the electrolysis of water. — When 
acidulated water is decomposed by the bat- 
tery current, the oxygen which is disen- 
gaged at the positive pole contains small 
quantities of ozone, and the proportion of 
the latter may be increased by adding a 
quantity of sulphuric or chromic acid to 
the water. 

3. During slow oxidation. — Some sticks 
of cleanly-scraped phosphorus are intro- 
duced into a bottle containing enough 
water to just about half immerse them, 
and the whole is agitated from time to 
time. In a short time the air in the bottle 
will be charged with a small quantity of 
ozone. 

According to Schonbein, who observed 
these facts, ozone is produced during all slow combustions. 
Thus, when oil of turpentine is exposed to the air under the 
influence of sunlight, it is slowly oxidized, and in becoming 
resinified, it becomes at the same time charged with a small 
quantity of ozone. 

Properties of Ozone. — Ozone possesses an intense and pecu- 
liar odor. Hautefeuille and Chappuis have liquefied it by al- 
lowing the strongly compressed gas to expand suddenly : the 
liquid is sky-blue, and the compressed gas has the same color, 
the tint being deeper as the temperature is lowered or the press- 
ure increased. At a temperature of 290° it is reconverted 
into ordinary oxygen, the volume of which is greater than that 
occupied by the ozone. It is then certainly condensed oxygen. 
It has energetic oxidizing properties ; it even oxidizes bodies 




Fig. 22. 



72 ELEMENTS OF MODERN CHEMISTRY. 

whicli possess only feeble affinities for oxygen. In the presence 
of alkalies it combines with nitrogen, converting it into nitric 
acid, which combines with the alkali. 

It oxidizes silver at ordinary temperatures, converting it into 
the dioxide Ag^O^ It instantly decomposes potassium iodide, 
setting free the iodine. It dissolves in about twice its vol- 
ume of water, and is quite readily soluble in oil of turpentine, 
which it slowly oxidizes. It oxidizes and destroys most or- 
ganic, substances. In most of these oxidations only a third 
part of the oxygen contained in ozone is active ; the other 
two-thirds become free as ordinary oxygen, the volume of 
which is exactly equal to that originally occupied by the ozone. 

Hence it is concluded that 3 volumes of oxygen are con- 
densed into 2 volumes by their conversion into ozone, and if 
ordinary oxygen be the oxide of oxygen 00, ozone will be oxy- 
gen peroxide 00'^ (Odling). 



0=0 = 2 vol. oxygen. / \ = 2 vol. ozone. 

0—0 

This conclusion of Odling's concerning the nature of ozone, 
has been verified by the determination of the density of this 
body. Soret has established that when ozone diluted with oxy- 
gen is absorbed by oil of turpentine or oil of cinnamon, there 
is a diminution of volume sensibly double the increase of 
volume noticed on subjecting the same gas to the action of 
heat. He naturally concludes that the density of ozone is one 
and a half times that of oxygen, or 1.658. These figures have 
been confirmed by direct experiments upon the rapidity of 
diffusion of ozone. It has been shown by the researches of 
G-raham that when diffusion between two gases takes place 
through an opening, without the interposition of a diaphragm, 
the rapidity of diffusion is inversely as the square roots of the 
densities of the gases. Soret has demonstrated that the 
rapidity of diffusion of ozone is notably greater than that of 
chlorine, and very near but somewhat less than that of car- 
bonic acid. It follows that its density is less than that of 
chlorine, and a little greater than that of carbonic acid, which 
is 1.525 ; this confirms the density 1.658. 

An important property of ozone is its reaction with hydrogen 
dioxide, yielding ordinary oxygen and water. 

00^ 4- H^O^ = 2(00) + H^O 

Ozone. Hjdrogen dioxide. Ordinary oxj'geii. Water. 



THE ATMOSPHERE. 



73 



ATMOSPHERIC AIR. 

The air is a mixture of oxygen and nitrogen. It also con- 
tains a little less than one per cent, by volume of a gas recently 
discovered by Lord Rayleigh and Professor Ramsay, and named 
by them argon^^ traces of carbonic acid gas, and a variable 
proportion of vapor of water. 

Its composition was established by Lavoisier by an experi- 
ment that has become celebrated. Having heated mercury in 
a limited quantity of air to a temperature near its boiling-point 
for several days, he observed the formation of a red powder, a 
combination of the mercury with oxygen. On the termination 
of the experiment, he found that the volume of the air had 
diminished about one-sixth. He carefully collected the oxide 
formed, introduced it into a small retort, 
and heated it to redness. He thus ob- 
tained a gas " eminently qualified to sup- 
port combustion and respiration," and the 
volume of which was sensibly equal to 
that of the gas that had disappeared. This 
gas he named oxygen. He mixed it with 
the irrespirable residue from the first ex- 
periment, which would not support com- 
bustion, and so reconstituted atmospheric 
air. The composition of the latter was 
thus established by analysis and synthesis. 
This experiment was infinitely more in- 
structive than that undertaken by Scheele 
at about the same time. The great Swedish 
chemist only absorbed the oxygen of the 
air by the alkaline sulphides. The nitrogen 
remained as residue, but the oxygen com- 
bined with the sulphide could not be again 
separated. 

However, neither one nor the other of Fig. 23. 

these methods could give the exact propor- 
tion according to which the oxygen and nitrogen are mixed in 
the atmosphere. This has been deduced from experiments 
like the following. 




1 In the analysis of air by the methods to be presently described, the 
argon remains mixed with the nitrogen. 

D 7 



74 



ELEMENTS OF MODERN CHEMISTRY. 



Experiments. — 1. A straight glass tube closed at one end 
(Fig. 23) is graduated as exactly as possible into five parts 
of equal capacity by caoutchouc bands placed around the tube. 
A dry piece of phosphorus, about half a cubic centimetre in 
volume, is dropped into the tube, the latter is tightly corked, 
and the phosphorus inflamed by plunging the end of the tube 
into hot water. By rapidly inverting the tube and tapping 
the corked end on the table the ignited phosphorus is caused 
to fall the whole length of the tube, and 
in burning consumes all the oxygen of the 
contained air. The tube is allowed to cool, 
and the cork is withdrawn under colored 
water in a beaker. The water rises to the 
first band, showing that 
the oxygen gas removed 
constituted about one- 
fifth of the air in the 
tube. The gas remain- 
ing in the tube is prin- 
cipally nitrogen. 

2. 100 volumes of 
air are measured into a 
graduated tube on the 
mercury-trough. A con- 
centrated solution of 
potassium hydrate is 
introduced, and then 
some pyrogallic acid, a 
white, crystalline sub- 
stance employed in pho- 
tography. The ex- 
tremity of the 
tube is now 
closed by the 
thumb and the 
contents rapidly 
agitated. The 
alkaline solution 
is immediately blackened by the oxidation of the pyrogallic 
acid. All the oxygen is absorbed, and when the tube is 
opened, under the surface of the mercury, the 100 volumes 
of air are found reduced to about 79 volumes, and the experi- 




FiG. 24. 



THE ATMOSPHERE. 75 

ment shows that the air contains about 21 per cent, by volume 
of oxygen. 

3. 50 cubic centimetres of air are measured off in a Hempel 
gas burette (6, Fig. 24) and transferred to the explosion pipette, 
r, by raising reservoir-tube D. In the same manner 50 cubic 
centimetres of pure hydrogen are introduced. The stop-cock 
S and the clip d are now closed, and by means of the plati- 
num electrodes P, which are fused through the walls of the 
pipette, a spark from an induction coil is sent through the gase- 
ous mixture. A flash is observed and all the oxygen contained 
in the air combines with hydrogen to form water. The residual 
gas is returned to the burette and measured : it is found to 
have undergone a considerable contraction in volume, and one- 
third of this contraction represents the volume of oxygen con- 
tained in the sample of air taken, for two cubic centimetres of 
hydrogen disappear for each cubic centimetre of oxygen. 

It is found that of the 100 cubic centimetres of gas in- 
troduced into the apparatus, 31.395 cubic centimetres have 
disappeared, showing that the 50 cubic centimetres of air intro- 
duced into the apparatus contained 10.465 cubic centimetres 
of oxygen. The remaining 39.535 cubic centimetres consist 
of nitrogen mixed with 1.186 per cent, of argon, and a trace 
of carbonic acid. 

Hence 100 volumes of air contain practically 20.93 volumes 
of oxygen and 79.07 volumes of nitrogen. 

Such is the composition of the air by volume. As nitrogen 
is lighter than oxygen, these volumetric relations do not express 
the composition of the air by weight. This was determined 
very exactly by Dumas and Boussingault in the following 
manner. 

A globe, A (Fig. 25), having a capacity of 15 or 20 litres, 
and fitted with a brass cap and stop-cock, R", by which it may 
be connected with an air-pump, is joined to a hard glass tube, 
BB'. having a stop-cock at each end, II and E,', and filled with 
metallic copper. The air is exhausted from the globe and tube, 
and the weight of each is then accurately determined. 

The tube BB' is placed in a combustion-furnace, and by its 
extremity B' is connected with the tubes K, I, H, G, F, E, D, 
C. The tube with bulbs C contains a solution of caustic 
potash ; the tubes D and E are filled with pumice-stone impreg- 
nated with caustic potash, and the tubes F and G with frag- 
ments of solid caustic potash ; the bulbs H contain sulphuric 



76 



ELEMENTS OE MODERN CHEMISTRY. 



acid, and the last tubes, I and K, are filled with fragments of 
pumice-stone saturated with sulphuric acid. The potash serves 

to remove from the air 
the small quantity of 
carbonic acid gas which 
it contains, and the sul- 
phuric acid absorbs the 
moisture. 

The tube filled with 
copper is now heated to 
redness, its stop-cocks 
being open, and the 
stop-cock of the globe is 
gradually opened. Air 
immediately enters, but 
it is first obliged to tra- 
verse the series of tubes, 
where it is deprived 
of its carbonic acid 
gas and vapor of water, 
and also the tube filled 
with incandescent cop- 
per, which absorbs the 
oxygen. It is then pure 
nitrogen which enters 
the globe. The experi- 
ment has terminated 
when the tension of the 
gas in the globe is equal 
to the exterior pressure, 
that is, when no more 
air enters. The stop- 
cock E." is now closed. 
The tube and globe are 
allowed to cool, and are 
weighed separately. 

The increase in weight 

of the globe gives the 

weight of the nitrogen 

which has entered. 

The increase in weight of the tube, which was first weighed 

exhausted of air, gives the weight of the oxygen which has 




\ 



THE ATMOSPHERE. 77 

combined witli the copper, plus the weight of the nitrogen 
remaining in the tube at the close of the experiment. The 
weight of this nitrogen is determined by exhausting the tube 
and weighing a third time. The difference between the second 
and third weighings indicates the weight of the nitrogen re- 
maining in the tube at the end of the experiment, and this 
weight added to that of the nitrogen contained in the globe 
constitutes the total weight of nitrogen in the air analyzed. 

The weight of the oxygen is given by the difference between 
the third and first weighings of the tube. 

By this method Dumas and Boussingault found that 100 
parts of air contain by weight 

Oxygen 23.13 

Nitrogen 76.87 

These two gases are simply mixed in the air ; they do not 
exist there in a state of combination ; and the proportions of 
the mixture are universally the same with very slight varia- 
tions. At the summits of the highest mountains, at the centres 
of the continents, and over the vast expanse of the seas, the 
air has been shown to be nearly equally rich in oxygen. From 
a comparison of a great number of analyses, Regnault has es- 
tablished that as a rule the percentage of oxygen only varies 
from 20.9 to 21.0 ; air which has been collected on the open 
sea and close to the surface of the water, has been found to 
contain a somewhat smaller amount (20.6), a circumstance 
which may be attributed to the dissolving action of the water. 

Nitrogen and oxygen are by far the most abundant con- 
stituents of the atmosphere ; among the substances which are 
contained in small proportion must be mentioned particularly 
the new element argon, carbonic acid gas, and vapor of water. 

Argon, A = 40 ? — When the nitrogen obtained from air is 
absorbed by heated magnesium there remains a small unabsorb- 
able residue, which, when fully purified from all known ele- 
ments, appears to be entirely inert ; hence the name argon 
(apyov, idle, inactive). This new element was discovered by 
Rayleigh and Ramsay in 1894, and constitutes about 0.94 per 
cent, of air. It is colorless, has a density of about 20 com- 
pared to hydrogen, and has about the same solubility in water 
as oxygen. Its critical temperature is — 121°, and the critical 
pressure 50.6 atmospheres. The experiments thus far made 
show that it is incapable of combining or reacting with other 

7* 



78 



ELEMENTS OF MODERN CHEMISTRY. 



substances, and chemical activity is not excited in it even by 
the electric spark. 

Carbonic Acid Gas and Vapor of Water. — If lime-water 
be poured into a flat dish and exposed to the air, in a few 
hours its surface will be found covered with a white pellicle 
formed of little crystals of calcium carbonate. 

This experiment demonstrates the presence of carbonic acid 
gas in the atmosphere. The watery vapor may be condensed 
by exposing to the air a glass vessel containing a mixture of ice 
and salt. The sides of the vessel soon become covered with a 
layer of frost, resulting from the solidification of the water which 
has been condensed from the air by the cool surface of the glass. 

The exact quantities of carbonic acid gas and vapor of water 
contained in the air may be determined by drawing the latter 
through tubes containing sulphuric acid and caustic potash. 
The aspiration is obtained by means of a bottle or a tin vessel, 
V (Fig. 26), filled with water. On opening the stop-cock r. 




Fig. 26. 



the water runs out, and air is drawn in through the tubes F 
and E, filled with fragments of pumice-stone wetted with sul- 
phuric acid, then through D and C, containing pumice-stone 



THE ATMOSPHERE. 79 

impregnated with caustic potash, and jBnally B, which is like 
the first two. These tubes increase in weight from the absorp- 
tion of vapor of water in the first two, and carbonic acid in 
the others. The difference in weight of the tubes F and B 
before and after the experiment gives the proportion of con- 
densed water ; the difference of D, C, and B gives the propor- 
tion of carbonic acid gas. The volume of air is equal to that 
of the water which has run out of the aspirator. 

The quantity of carbonic acid gas contained in the air 
varies from 0.029 to 0.033 per cent. It is increased in in- 
habited places. It is greater at night than during the day, 
a circumstance that must be attributed to the influence of 
vegetation. It is diminished after a rain, and is found in its 
minimum proportion above the surface of large lakes. 

The sources of this carbonic acid gas are various. In cer- 
tain regions fissures in the earth disengage large volumes ; vol- 
canoes emit immense quantities ; certain spring waters are 
supersaturated, and disengage it in abundance when they reach 
the surface of the earth. But the greater portion is produced 
by the phenomena of combustion which take place on the 
earth's surface ; and among these phenomena must be included 
respiration, which is a slow combustion. 

Experiment. — If by the aid of a glass tube air from the 
lungs be blown through lime-water, the latter becomes clouded, 
by the formation of calcium carbonate. The carbonic acid gas 
thus fixed by the lime comes from the respiration, which is an 
abundant source of that gas. 

Does carbonic acid gas accumulate indefinitely in the atmos- 
phere ? No. Rejected and excreted by animals, it serves for the 
respiration of plants. The green parts of vegetables possess the 
power of decomposing this gas under the influence of the sun's 
light. The carbon is fixed, and serves for the nutrition of the 
plant ; the oxygen is rejected, if not wholly, at least in great part. 

Besides the constituents that have been enumerated, the 
air contains other matters in very minute proportions. These 
include : 

1. Traces of ammonia, or rather of ammonium compounds. These 
substances are dissolved by rain-water, and play an important part 
in vegetable physiology. 

2. A small quantity of nitric acid in the form of ammonium 
nitrate. It is supposed that nitric acid is formed in the air by the 
direct union of the nitrogen and oxygen under the influence of 
atmospheric electricity. In addition to this nitric acid, the air con- 



80 ELEMENTS OP MODERN CHEMISTRY. 

tains nitrous acid, also in the form of an ammonium salt, NH*NO^, 
and it is mainly from these compounds that most plants derive the 
nitrogen they require for their growth. 

3. A very minute and variable proportion of a substance which 
has the power of liberating iodine from potassium iodide, and which 
is generally believed to be ozone. 

4. Exceedingly small amounts of four gaseous elements, the exist- 
ence of which has only recently been made known by the researches 
of Eamsay and Travers. These new constituents of the air closely 
resemble argon : they appear devoid of chemical energy, and their 
molecules consist of single atoms. All four are, however, distinctly 
characterized by their spectra (see page 316), and they differ from 
one another also in their physical constants, such as density and 
boiling point. Krypton, Kr, has a density approaching 40, and is 
found in what remains when a large quantity of liquid air is evapo- 
rated to a small bulk. The other three are " Companions of Argon," 
being contained in different fractions of the gas given off when lique- 
fied crude argon is made to boil. Of these, neon, Ne, is the liglitest 
(density about 11) and most volatile, while metargon, A//, and xenon, 
X, are specifically heavier (approximate densities 20 and 64), and 
less volatile than even argon. 

5. Solid particles suspended in the air and carried to a distance 
by the winds. In perfectly calm air these corpuscles are deposited, 
forming a dust of which the composition is very variable. It con- 
tains various microscopic vegetable and animal germs (Pasteur). 



WATEK. 

Vapor density compared to air 0.621 

Vapor density compared to hydrogen 1 .... 8.94 
Molecular weight H^O =17.88' 

Water is the product of the combination of hydrogen and 
oxygen ; its composition v^^as established by Lavoisier in 1V83. 
The combination takes place exactly in the ratio of 2 volumes 
of hydrogen to 1 volume of oxygen, as demonstrated by the 
following experiments : 

1. Analysis of Water hy Electrolysis. — Water acidulated 

1 The density of vapor of water compared to that of hydrogen is 8.94; 
that is, if the weight of 1 volume of hydrogen be represented by 1, the 
weight of 1 volume of vapor of water will be 8.94 ; in other words, vapor 
of water is nearly nine times more dense than hydrogen under the same 
conditions of temperature and pressure. 

"^ The weight of the molecule, or the molecular weight, expresses the 
weight of 2 volumes of vapor, if the weight of 1 volume of hydrogen be 
represented by 1. 



WATER. 



81 



witli sulphuric acid is poured into the bulb of a Hofmann's 
electrolysis apparatus (Fig. 27) until it rises in the tubes to 
the level of the stop-cocks, which are open. The latter are 
then closed, and by means of platinum wires fused through the 
glass and connected with two platinum plates, one in each limb 
of the tube, a current from a galvanic battery is passed through 
the liquid in the bend of the tube. Water is decomposed and 
bubbles of gas arise in each tube, collect together, and force 




Fig. 27. 



the liquid up into the bulb. It soon appears that the gas dis- 
engaged at the negative pole is sensibly double in volume that 
disengaged at the positive. The first is hydrogen, and the 
second oxygen, and the proportion in which these gases are set 
free would be exactly that of 2 to 1, were it not that a small 
quantity of oxygen remains dissolved in the acid liquid, or, 
under certain conditions, combines with a portion of the water 
surrounding the negative pole to form hydrogen dioxide, as 
will be mentioned farther on. 

/ 



82 ELEMENTS OF MODERN CHEMISTRY. 

2. Eudiometric Synthesis. — The composition of water can 
be establislied by synthesis., tliat is, by tbe combination of tbe 
two elements, hydrogen and oxygen. The experiment, which 
is made in an eudiometer, has already been described (page 38). 
It demonstrates that the two gases combine in the exact ratio 
of 2 volumes of the first to 1 of the second, and that these 
3 volumes of gas are condensed into 2 volumes of vapor of 
water. 

These experiments establish the volumetric composition of 
water ; its composition by weight can be deduced from them, 
the densities of hydrogen and oxygen being known ; for the 
weighable matter of 2 volumes of hydrogen being added to the 
weighable matter of 1 volume of oxygen, it is only necessary 
to add twice the weight of 1 volume of hydrogen to the weight 
of 1 volume of oxygen in order to determine the weight of 2 
volumes of vapor of water. That is to say, the ratio by weight 
in which hydrogen combines with oxygen to form water is that 
of double the density of hydrogen (the weight of 2 volumes of 
H) to the density of oxygen (the weight of 1 volume of 0). 
This ratio is 

2 X 0.0695 _ 0.1390 _ 1 
1.1015 1.1015 7.94 

It may be deduced in a more simple manner by a compari- 
son of the densities of hydrogen and oxygen. If 1 volume 
of hydrogen weighs 1, 1 volume of oxygen weighs 15.88 ; the 
weight of 2 volumes of hydrogen will then be 2, and it will 
be seen that the two gases unite, by weight, in the ratio of 

2 ^ 1 
15.88 7.94 

17.88 grammes of water then contain 15.88 grammes of 
oxygen and 2 grammes of hydrogen. This composition of 
water by weight has also been ascertained by various other 
methods, of which that employed by Dumas has become 
classic, and will now be described. 

3. Synthesis of Water hy the Gravimetric Method. — In order 
to determine the composition of water by synthesis it is suffi- 
cient to combine an indeterminate quantity of hydrogen with 
a precisely determined weight of oxygen, and to weigh exactly 
the water formed. By subtracting from this latter weight that 



WATER. 



83 



of the oxygen contained in the water, the weight of the hydro- 
gen which has com- 
bined with that oxy- 
gen is obtained. 

In order to thus 
combine hydrogen 
with oxygen, it is 
convenient to make 
the former gas react 
upon an oxidized 
body which will read- 
ily yield its oxygen 
to the combustible 
gas. Cupric oxide, or 
black oxide of cop- 
per, CuO, first sug- 
gested by Gray-Lus- 
sac, and employed for 
this purpose by Ber- 
zelius and Dulong, 
fulfils these condi- 
tions. Although un- 
decomposable by heat 
alone, it is readily re- 
duced by hydrogen 
when heated in an at- 
mosphere of that gas. 
Dumas employed the 
apparatus represent- 
ed in Fig. 28. 

Hydrogen is pre- 
pared by the action 
of dilute sulphuric 
acid upon zinc, and 
is purified by being 
conducted through a 
series of U tubes, the 
first containing frag- 
ments of glass wet 
with a solution of lead 
acetate, the second, 
fragments of glass wet with a solution of silver sulphate, and 




84 ELEMENTS OF MODERN CHEMISTRY. 

the third, pumice-stone, impregnated witli caustic potassa. 
The lead acetate retains hydrogen sulphide ; the silver sulphate 
absorbs hydrogen arsenide, and the potassa absorbs any traces 
of carbides of hydrogen. 

The hydrogen thus purified is dried by passage through an- 
other series of U tubes, the first containing calcium chloride, 
and the others pumice-stone saturated with sulphuric acid. The 
latter tubes are cooled by being surrounded with ice. The gas 
is lastly passed through a smaller tube containing phosphoric 
oxide. The weight of this tube must remain constant during 
the whole of the experiment. It is called the control-tube. 

The pure and dry hydrogen now passes through a hard 
glass bulb, which contains pure cupric oxide. The weight of 
this bulb, together with the oxide which it contains, is deter- 
mined with care. The receiver B', as well as the U tubes 
which terminate the apparatus, are also accurately weighed. 

When the whole of the air contained in the apparatus has 
been expelled by the hydrogen, the bulb is heated and the 
cupric oxide is reduced. Water is formed and is in great part 
condensed in the liquid state in the receiver, but a portion of 
the vapor remains uncondensed and is carried off by the excess 
of hydrogen. This vapor is retained in the second series of 
U tubes, which contain calcium chloride and pumice-stone satu- 
rated with sulphuric acid. When the reduction has almost 
terminated, the bulb is allowed to cool, the current of hydro- 
gen being continued ; this gas is finally displaced by a current 
of air, and the weighings are then made. 

The weight of the bulb has decreased by that of all of the 
oxygen which has been taken from the oxide of copper by the 
hydrogen, and which now exists in the water formed. 

The weight of the receiver and the condensing apparatus con- 
nected with it is increased by the weight of all the water formed. 

By subtracting the weight of the oxygen from that of the 
water we find the weight of the hydrogen. 

By the aid of this rigorous method it is found that 100 
parts by weight of water contain^ 

Hydrogen 11.18 

Oxygen 88.82 

100.00 

1 The figures given are slightly different from those obtained by Dumas. 
They represent the mean results of more recent investigations by Ray- 
leigh, Scott, Morley, and others. By uniting oxygen and hydrogen di- 
rectly, and weighing the gases before they combine, as well as the water 
produced, Morley has achieved completeness in this gravimetric synthesis. 



WATER. 85 

These numbers are in the exact ratio of 

Hydrogen 1 

Oxygen 7.94 

Physical Properties. — Pure water has neither taste nor 
odor. It is limpid and colorless. It occurs in three states in 
nature ; during the colds of winter it is solid, assuming the differ- 
ent forms of ice, snow, frost, and hail. The temperature at 
which ice melts is one of the standard points in the thermo- 
metric scale. To this temperature corresponds the of the cen- 
tigrade scale, which is adopted in this work. 

Snow consists of aggregations of minute hexagonal crystals 
like those shown in Fig. 29. 



Fig. 29. 

At the moment of freezing, water expands, and its density- 
is then less than that which it possesses in the liquid state. 
The density of ice is 0.93. Water contracts in volume from 
to -j- 4°, and presents its maximum density at the latter tem- 
perature. Its density at this point is chosen as the unit of 
comparison for the densities of solid and liquid bodies. 

Water and even ice are continually emitting invisible vapors 
which mix with the air, and are, as it were, dissolved in it. 
This vaporization increases as the temperature is raised. 

The air is said to be saturated with vapor at any given tem- 
perature when it refuses to take up any more vapor at that 
temperature. Under these conditions, if the temperature be 
lowered, a portion of the vapor is condensed in fine drops, 
which remain suspended in the air in the form of mist or visi- 
ble vapor. The point at which the moisture of the air is con- 
densed is called the dew-point. 

Water begins to boil when its vapor acquires sufficient ten- 
sion to overcome the atmospheric pressure. This is the boil- 
ing-point, and under a pressure of 0.760 metre corresponds to 
100° of the centigrade scale. 

8 



86 



ELEMENTS OF MODERN CHEMISTRY. 



Chemical Properties. — Water is partially decomposed by 
the highest temperatures at our command. On pouring melted 
platinum into an iron mortar containing water, &rove observed 
a disengagement of bubbles composed of an explosive mixture 
of oxygen and hydrogen. According to H. Sainte- Claire De- 
ville, vapor of water undergoes a partial decomposition, which 
he calls dissociation^ when exposed to a temperature between 
1100 and 1200°. In order to collect the gases resulting from 
this decomposition it is necessary to separate them before they 
have reached a part of the apparatus where a less elevated 
temperature would permit their recombination. For this pur- 
pose Deville directed a current of steam through a porous clay 
tube, a (Fig. 30), surrounded by a tube of glazed porcelain, h, 




Fig. 30. 



which was heated to whiteness in a powerful furnace. A cur- 
rent of carbonic acid gas was passed through the annular space 
between the two tubes, by means of the tube c. The vapor of 
water was decomposed by the heat into hydrogen and oxygen ; 
but these two gases separated from each other : the hydrogen, 
being the more diffusible, passed in great part through the 
porous tube, while the oxygen was delivered by the interior 
tube, together with a small quantity of carbonic acid gas, which 
entered by diffusion. The gases evolved by the two tubes were 
collected in a small jar filled with a solution of caustic potash 
by which the carbonic acid gas was absorbed, and there re- 
mained an explosive mixture of hydrogen and oxygen. 

Water is decomposed by an electric current, as already seen. 



WATER. 87 

It is likewise decomposed by many of the elements, metallic 
and non-metallic, which combine with one or the other of its 
component elements. Thus, chlorine decomposes it at a red 
heat, uniting with the hydrogen to form hydrochloric acid, and 
setting free the oxygen ; also under the influence of light at 
ordinary temperatures. A number of the metals decompose 
water, liberating the hydrogen. 

Iron decomposes it at a red heat, taking up the oxygen and 
setting free the hydrogen ; potassium and sodium, as we have 
seen in the case of the latter metal, produce the same effect at 
ordinary temperatures. 

Many compound bodies seize upon the elements of water, 
and are decomposed by it. Such are the chlorides of phos- 
phorus and antimony. In these reactions, which will be 
studied farther on, the hydrogen of the decomposed water 
unites with the chlorine, the oxygen with the other element. 

We have already noticed the action of water upon the non- 
metallic and metallic oxides. It combines with many of these 
compounds, forming hydroxides^ which are either acid or basic. 
Certain of these reactions are worthy of reconsideration. It 
is especially important to fully appreciate the part played by 
the water which enters into them. 

When potassium oxide becomes hydrated to form caustic 
potash, the reaction takes place by a double decomposition, 
which may be expressed by the following equation : 

(1)|}0 + |}o = g}o + l]o 

Potassium oxide. Water. Potassium hydroxide. Potassium hydroxide. 

It will be seen that both the potassium oxide and the water 
are converted into potassium hydroxide by the exchange of an 
atom of potassium for an atom of hydrogen. Potassium hydrox- 
ide is, as it were, derived from water by the substitution of an 
atom of potassium for an atom of hydrogen. This substitution 
takes place directly when water is decomposed by potassium. 

(2) 2W0 -f K^ = 2K0H + H^ 

The potassium hydroxide in its turn may lose the remaining 
atom of hydrogen ; if it be heated with potassium, this hydro- 
gen is displaced, and potassium oxide is formed. 

(3) 2K0H + K^ = 2K20 -f H^ 

Potassium hydroxide. Potassium. Potassium oxide. Hydrogen. 



88 ELEMENTS OF MODERN CHEMISTRY. 

It will be seen from what precedes that, starting with water, 
we may form potassium hydroxide (2), potassium oxide (3), and 
this again may be converted into potassium hydroxide (1). The 
three compounds are then closely related. Each contains 1 
atom of oxygen combined with 2 atoms of another body, hy- 
drogen or potassium, and the relation is clearly expressed in 
the following formulae : 

i}o i}o |}o 

Water. Potassium hydroxide. Potassium oxide. 

If hypochlorous oxide, CPO, be poured into water, it is in- 
stantly dissolved and converted into hypochlorous acid. The 
reaction is expressed in the following equation : 

^l}o + g}o = ^^o + o'}o 

Hypochlorous oxide. Water. Hypochlorous acid. Hypochlorous acid. 

Both the hypochlorous oxide and the water are converted 
into hypochlorous acid by the exchange of an atom of hydro- 
gen for an atom of chlorine, so that the hypochlorous acid 
may be said to represent water in which 1 atom of chlorine is 
substituted for an atom of hydrogen. 

Thus, by their atomic constitution both potassium hydroxid-e 
and hypochlorous acid are closely related to water. But on 
comparing them together they are found to differ widely in 
their properties, both from each other and from water itself. 
How could it be otherwise with bodies containing elements as 
unlike as potassium and chlorine ? Indeed, the distance which 
separates potassium hydroxide and hypochlorous acid is not 
greater than that which separates potassium and' chlorine. 
Thus, a difference of elements may imply a marked difference of 
properties between bodies which otherwise present a similar con- 
stitution, and which may be said to belong to the same fi/pe. 

Water is one of these types. Its constitution serves as a 
sort of model for that of a multitude of compounds. It will be 
sufficient to reconsider the examples already cited, and we may 
say that water, potassium hydroxide, potassium oxide, hypo- 
chlorous acid, and hypochlorous oxide belong to the watei' type. 



S'l" 


^'}o 


g}o 


S!o 


i]" 


ypochlorous 


Hypochlorous 


Water, 


Potassium, 


Potassium 


oxide. 


acid. 




hydroxide. 


9xide, 



WATER. 89 

The preceding considerations give but a limited idea, but 
one sufficient for the present, of the role played by water in 
chemical phenomena. This role is one of great importance, 
for water takes part in an immense number of reactions, either 
by its decomposition, its formation, or its combination. 

Water presents still another mode of action. It dissolves 
very many bodies, and this solvent action is exerted upon 
gases, liquids, and solids. 

Solvent Properties of Water. — When a gas dissolves in 
water, it changes its state, it becomes itself liquid, and in lique- 
fying it evolves heat. In the same manner a solid body be- 
comes liquid by the act of solution, but in order to become 
liquid it must absorb heat. Consequently, the solution of a 
gas in water takes place with a production of heat ; that of a 
solid body takes place with a lowering of temperature, or, to 
use a common expression, a production of cold. 

But sometimes this physical phenomenon of the solution of 
a solid body in water, that is, its liquefaction and diffusion in 
the liquid, is complicated by a chemical action. 

Experiment. — If water be poured upon dried and powdered 
calcium chloride, the salt is instantly dissolved with a produc- 
tion of heat. This heat is the evidence of a chemical com- 
bination, and the water has indeed combined with the calcium 
chloride ; if now the solution be sufficiently evaporated, it will 
deposit fine transparent crystals of hydrated calcium chloride. 
The water contained in these crystals, and which is necessary 
for their formation, is what is called water of crystallization. 
It is contained in definite proportions, and is retained in the 
crystals by affinity. For this reason the combination of water 
with calcium chloride is accompanied by a production of heat. 

If these crystals of calcium chloride be dissolved in water, 
they disappear, and the temperature of the liquid is depressed. 
The physical phenomenon of the solution of a solid body in 
water can thus be separated from the chemical phenomenon 
of its combination with that liquid. 

Natural State of Water. — Water is not met with in a pure 
state in nature. Whether it has rested upon or has flowed over 
the surface of the soil, whether it has fallen in the form of rain, 
mist, or dew, or whether it has just issued from its subterranean 
passages, it always contains various matters in solution. 

It takes up the gases from the atmosphere, and also certain 
bodies which it there finds suspended or in vapor. On the 

8* 



90 ELEMENTS OF MODERN CHEMISTRY. 

surface or in the bosom of the earth it dissolves the soluble 
substances which it encounters. Hence the composition of 
natural water presents great variations, according to the origin 
of the water and the localities where it has collected, or the 
soils through which it has travelled. In general, meteoric 
waters, that is, those which result from the condensation of 
the aqueous vapor diffused through the atmosphere, are more 
pure than those which have collected upon the earth's surface. 
The latter present in their physical and chemical properties, in 
their composition, and in their action upon the animal econ- 
omy, such differences that they are classified in several groups. 

Soft or potable waters are distinguished from hard waters. 
The first are such as hold only small quantities of foreign mat- 
ters in solution, and are essentially fit for domestic use. The 
second are too highly charged with saline matters, and princi- 
pally the salts of calcium, to be fit for such purposes. Grood 
potable water should be cool, limpid, without odor, should have 
a faint but agreeable taste, which should be neither insipid, 
saline, nor sweet, and should cook and soften vegetables and 
dissolve soap. The purest water is not necessarily the best. 
Thus distilled water, rain-water, and that comins; from the 
melting of ice and snow, although more pure, are less salubrious 
than good spring or river water. 

Good potable water should be aerated, that is, it should hold 
in solution the gases contained in the atmosphere : oxygen, 
nitrogen, and carbonic acid. E-ain-water takes from the atmos- 
phere a proportion of oxygen, and especially of carbonic acid 
gas, much greater than that in which these gases are contained 
in the air. This must be so, for Dalton has shown that the 
solvent action of water upon a gaseous mixture is measured for 
each gas by the product of its coefficient of solubility and the 
figure expressing the proportion of that gas in the mixture 
These gases are driven out of water by boiling. 

The following figures give the proportions of the atmospheric 
gases expelled by boiling from a litre of water from the Seine, 
the same quantity from the Delaware, and also the proportions 
contained in a litre of rain-water : 

Water of the Seine Water of the Dela- Rain-Waterin Jan. 



Carbonic acid gas . 

Nitrogen 

Oxygen 


in January. 
. 22.6 c.c. 
. 21.4 
. 10.1 

54.1 


ware m July. 
1.6 c.c. 
12.2 
5.3 

19.1 


0.5 c.c. 1.77 

15.1 64.47 

7.4 33.76 

23.0 100.00 



WATER. 91 

It is seen that at the same season the running water con- 
tains a larger amount of all of the gases than rain-water, and 
a notably larger proportion of carbonic acid. 

Solid Matters dissolved in Water. — Soft waters generally 
contain a small proportion of fixed matters, among which are 
certain salts of calcium and magnesium, certain alkaline salts, 
silica, and organic matters. 

The calcium salts are the carbonate and sulphate, and some- 
times traces of the chloride, nitrate, and phosphate. 

Calcium carbonate, or carbonate of lime, is almost insoluble 
in pure water, but dissolves readily in water charged with 
carbonic acid gas ; in such solutions it exists as dicarbonate. 
When water thus charged with calcium dicarbonate is boiled, 
that salt is decomposed, carbonic acid gas is disengaged, and 
neutral calcium carbonate is precipitated. When the propor- 
tion of calcium dicarbonate contained in spring-water is large, 
it may happen that as the water loses carbonic acid gas the 
calcium carbonate is deposited at ordinary temperatures. This 
efibct is favored by the tumultuous movements to which spring- 
water is subjected either in flowing over an inclined bed or in 
conducting-pipes. The carbonate then forms a crystalline de- 
posit, which incrusts the interior walls of the pipes and, in 
general, whatever objects may be plunged into such waters, 
which for this reason are called incrusting or petrifying waters. 

The presence of small quantities of calcium dicarbonate in 
drinking-water may be considered as a good condition, from a 
hygienic stand-point, for the system needs calcareous salts for 
the development and nutrition of th 3 bony structures. 

Calcium suljjJiate, or sulphate of lime, exists in solution in 
many waters, especially in spring and well waters. When the 
proportion does not exceed fifteen or twenty centigrammes per 
litre, such water may be used without inconvenience for do- 
mestic purposes. Water largely charged with calcium sulphate 
is called selenitous water ; it does not become clouded on ebul- 
lition. Like all other strongly calcareous water, it does not dis- 
solve soap without first forming a flocculent precipitate. Salts 
of barium produce with such water an abundant white precipi- 
tate of barium sulphate, which is insoluble in nitric acid. Such 
water is unfit for economic purposes. In geueral, the propor- 
tion of calcareous salts in potable water should not exceed five 
or six decigrammes per litre ; water containing more than this 
is difl&cult to digest, and is called hard water. Potable water 



92 ELEMENTS OF MODERN CHEMISTRY. 

should not contain more than mere traces of organic matter. 
If the organic matter be due to sewage, the water yields am- 
monia when boiled with an alkaline solution of potassium per- 
manganate : more than 0.10 per million of such ammonia indi- 
cates an unwholesome water. 

Mineral or Medicinal Waters. — These are waters that by 
virtue of their temperature or chemical constituents exercise 
a special action upon the animal economy, and consequently 
have a therapeutic value. 

^ They are cold or warm. They are called warm when their 
temperature at the moment of emergence is above 20°. Their 
temperatures vary greatly, and may rise to the boiling-point 
of water. The temperature of the Grrand Geyser in Iceland 
is even above 100° in the depths of the tube from which it 
issues. According to their constituents, mineral waters are 
classified as follows : 

Acidulous or gaseous waters^ characterized by the presence 
of free carbonic acid. 

Alkaline waters^ characterized by the presence of sodium 
dicarbonate, or of an alkaline silicate. 

Clialyheate waters^ holding a salt of iron in solution. 

Saline waters^ or those containing certain neutral salts. 

Sulphur waters, characterized by the presence of hydrogen 
sulphide or other soluble sulphide. 

On arriving at the surface of the earth, certain of these 
mineral waters undergo a change in chemical constitution. 
Such are the sulphur waters which absorb oxygen, as will be 
noticed presently. Those containing free carbonic acid lose a 
part of their gas, and it often happens that some of the car- 
bonates held in solution by an excess of carbonic acid become 
insoluble, and are deposited after the escape of that excess. 
This is the principal cause of the deposits which form in the 
basins and conducting-pipes of many mineral waters. These 
deposits vary greatly in composition ; sometimes they are floc- 
culent or pulverulent, and collect in the form of mud ; some- 
times they form hard concretions or scales. Calcium and 
magnesium carbonates, ferric hydrate, alumina, and silica are 
the most ordinary constituents of such deposits. Besides these, 
arsenic, various metallic oxides, and materials which it would 
be difficult to detect in the water itself, are sometimes concen- 
tratedj as it were, in these deposits. Thus, arsenic is detected 



WATER. 93 

mucli more readily in the oclirey deposits around a ferraginous 
spring than in the water of the spring itself. 

Acidulous or GtASeous Waters. — Free carbonic acid is 
the characteristic and predominant element of these waters ; it 
is dissolved in the depths of the earth under a pressure much 
greater than that of the atmosphere ; hence a certain portion 
of the gas is disengaged as soon as the water emerges from the 
soil, giving rise to a greater or less effervescence. Graseous 
waters are cold ; their taste is piquant at the moment of emer- 
gence, but often becomes saline or even alkaline after the dis- 
engagement of the greater part of the carbonic acid gas. Nat- 
ural gaseous waters never consist of a solution of carbonic 
acid in pure water ; they always contain a small quantity of 
saline matters, principally traces of sodic, calcic, and magnesic 
carbonates, and even traces of chlorides and sulphates. Such 
is the composition of the celebrated Seltzer water and of Soultz- 
matt water. The water of certain of the Saratoga springs 
approximates in composition to Seltzer water. 

Alkaline Waters. — These waters possess an alkaline re- 
action, either immediately on their emergence or after the loss 
of their free carbonic acid. This reaction may be due to an 
alkaline silicate, but is generally referable to an alkaline car- 
bonate. Sodium acid carbonate, NaHCO^, commonly called 
bicarbonate of soda, exists in nearly all waters of this class, 
together with an excess of carbonic acid. Vichy water con- 
tains about 5 grammes of this salt per litre. 

Chalybeate Waters. — Nearly all waters contain traces 
of iron in solution ; chalybeate waters are such as contain 
sufficient of that metal to give them an astringent taste and 
special therapeutic properties. The iron may exist in three 
conditions : 

1. As ferrous carbonate held in solution by carbonic acid. 

2. As ferrous crenate. Berzelius gave the names crenic 
and apocrenic acids to two bodies which are related to peculiar 
acids existing in the soil or humus, and which are known as 
ulmic, humic, and geic acids. Ferrous crenate is soluble in 
water ; its constitution is not known. 

3. As ferrous sulphate. 

Consequently, chalybeate waters may be carbonated, cre- 
nated, and sulphated. 

The ferrous salts are never contained in these waters in large 
proportions. Many ferruginous waters of undoubted efficacy 



94 ELEMENTS OP MODERN CHEMISTRY. 

do not contain more than 4 or 5 centigrammes per litre. 
When ^ exposed to the air they lose the greater part of their 
carbonic acid, and ferrous carbonate is deposited, but this loses 
its carbonic acid and is converted into brown ferric hydrate. 
Such is the manner of formation and the nature of the ochrey 
deposits always noticeable around ferruginous springs. 

Chalybeate waters are widely diffused. Those of Spa, Bel- 
gium, and Pyrmont (carbonated), Bussang in the Yosges. and 
Forges (crenated), and Passy, at Paris, are well known. Cele- 
brated springs of this class exist at Bedford, Pennsylvania, Mani- 
tou, Colorado, and indeed in many localities in the United States. 

Saline Waters. — This class includes a great number of 
waters charged with various neutral salts, among which are the 
chlorides, bromides', and iodides. The salts of sodium, mag- 
nesium, and calcium are those more usually met with in these 
waters. According to the predominating or peculiarly active 
principle present, they are classified as chlorinated, sulphated, 
and bromo-iodated waters. The Saratoga springs yield an 
acidulo-saline water. 

Chlorinated Saline Waters. — The chlorides generally found 
in mineral waters are those of sodium, magnesium, and cal- 
cium ; the former is much the more abundant, and constitutes 
one of the most common constituents of mineral waters. It 
communicates to them a pure salty taste, free from bitterness. 
A great number of saline springs serve for the extraction of 
sodium chloride. After the evaporation of the water and the 
deposition of the salt, a mother-liquor remains in which various 
less abundant salts are concentrated, principally the alkaline 
bromides and iodides. 

Sea-water is a chlorinated water. It is well known that it 
contains a notable proportion of sodium chloride (2.5 to 2.7 
per cent.). The common salt is accompanied by the chlorides 
of magnesium and potassium, and by a considerable quantity 
of magnesium sulphate (0.6 to 0.7 per cent.). 

The Dead Sea and the Great Salt Lake of Utah are the 
most concentrated natural saline waters. The water of the 
latter contains 20 per cent, of sodium chloride. 

Sulphated Saline Waters. — These are characterized by so- 
dium, magnesium, or calcium sulphate. The springs of Carls- 
bad, in Bohemia, contain a large proportion of sodium sulphate, 
together with sodium bicarbonate and sodium chloride. 

The purgative waters of Epsom, England, contain magne- 



HYDROGEN DIOXIDE. 95 

sium sulphate. The waters of Hunyadi, Friedrichshall, and 
Seidlitz contain magnesium sulphate and sodium sulphate. 
Their taste is bitter. The Avon Spring, New York, is of this 



Bromo-iodated Waters. — Many mineral waters contain small 
quantities of bromides and iodides, independently of the chlo- 
rides which generally exist in much larger proportions. The 
water of the Dead Sea, so rich in magnesium and sodium 
chlorides, contain 0.43 per cent, of magnesium bromide. The 
Iodine Spring at Saratoga contains a notable proportion of 
alkaline iodides. 

Sulphur Waters. — By this name are designated those 
waters containing a soluble sulphide or sulphuretted hydro- 
gen. They are either natural sulphur waters or accidental 
sulphur waters. The first contain sodium sulphide ; they are 
generally warm, and contain but little solid matter. They all 
disengage nitrogen on their emergence from the soil. They 
contain a nitrogenized organic matter (baregine), and some- 
times deposit a gelatinous precipitate (glairine). 

Celebrated springs exist in the Pyrenees, at Bagn^res-de- 
Luchon, and at Aix la Chapelle. The sulphur springs of 
Sharon and Avon, in New York, and the Bed and White 
Sulphur Springs of Virginia are well known. 

Accidental sidphur waters are those which are formed upon 
the spot by the reduction of sulphates, and particularly calcium 
sulphate, contained in the waters. This reduction is accom- 
plished by the action of organic matters which impregnate the 
soil, and of which the combustible elements, carbon and hydro- 
gen, remove the oxygen of the sulphates. It is thus that the 
sulphur water of Enghien is formed at the gates of Paris. 

HYDBOaEN DIOXIDE. 

H202 

This remarkable compound was discovered by Thenard in 
1818. It is formed by the action of barium dioxide upon di- 
lute hydrochloric acid. Barium dioxide, powdered and made 
into a fine paste with water, is introduced by small portions 
into cold and dilute hydrochloric acid. It dissolves without 
disengagement of gas, yielding barium chloride and hydrogen 
dioxide. 

BaO^ + 2HC1 = BaCP -{- H^O' 

Barium dioxide. Hydrochloric acid. Barium chloride. Hydrogen dioxide. 



96 ELEMENTS OP MODERN CHEMISTRY. 

The barium chloride is converted into insoluble sulphate by 

the cautious addition of dilute sulphuric acid, and hydrochloric 

acid is regenerated, so that an additional quantity of barium 

dioxide may be added ; this operation is several times repeated. 

BaCP + H^SO* = BaSO* + 2HC1 

Sulphuric acid. Barium sulphate. 

The barium chloride finally remaining in solution is exactly 
precipitated by a solution of silver sulphate, and the hydrogen 
dioxide solution poured off and evaporated in vacuo. For use 
in medicine and the arts dilute hydrogen peroxide is manufac- 
tured in considerable quantities by the reaction of hydrated 
barium dioxide with cold dilute phosphoric or sulphuric acids. 

Pure hydrogen dioxide is a syrupy, colorless, odorless liquid, 
having a density of 1.499. It is very unstable, and readily 
gives up half of its oxygen, being converted into water. This 
decomposition takes place with a brisk effervescence when the 
dioxide is heated towards 100° ; it is also produced by contact 
with a great number of bodies, some of which are themselves 
unaltered, some oxidized, and others even reduced. Hence 
hydrogen dioxide enters into three classes of reactions. 

1. If a solution of hydrogen dioxide be poured into a test- 
tube containing manganese dioxide, the hydrogen dioxide is 
reduced with effervescence into water and oxygen. The man- 
ganese dioxide remains unchanged. Finely divided platinum, 
gold, silver, and carbon act in the same manner. 

2. Hydrogen dioxide energetically oxidizes arsenic and sele- 
nium to arsenic and selenic acids, and lead sulphide to lead sul- 
phate. 

PbS + 4:W0' = PbSO* + 4H^0 

Lead sulphide. Lead sulphate. 

3. Potassium permanganate, KMnO*, is a salt very rich in 
oxygen ; it dissolves in water, forming a solution having an 
intense purple color. If hydrogen dioxide be added to it, it is 
immediately reduced and decolorized. The oxygen from the 
decomposition of the hydrogen dioxide is in this case added to 
that from the reduction of the permanganate, and both are dis- 
engaged in the free state. 

If hydrogen dioxide be added to a solution of potassium di- 
chromate, the latter assumes a deep blue color, but this rapidly 
disappears, giving place to a green tint. At the same time an 
evolution of oxygen takes place. In this case the reaction is 
complex : a portion of the hydrogen dioxide oxidizes the 



HYDROGEN DIOXIDE. 97 

chromic acid for an instant into blue percliromic acid, but the 
latter is instantly reduced, with disengagement of oxygen, by 
another portion of the hydrogen dioxide, which at the same 
time loses half of its oxygen. 

The oxygen gas liberated comes then at the same time from 
the perchromic acid and the hydrogen dioxide, both of which 
are supersaturated with oxygen, and which mutually reduce 
each other. The perchromic acid formed may be removed 
from the action of the excess of hydrogen dioxide by imme- 
diately agitating the liquid with ether : the latter dissolves the 
acid and assumes a dark-blue color. 

These experiments of reduction are of great interest, and 
permit of but one explanation. The fact of the reciprocal 
reduction of two bodies each supersaturated with oxygen can 
only be explained by admitting that the oxygen of one body 
possesses an affinity for that of the other, and that the oxygen 
which is set free is formed by the union of two atoms, one from 
the hydrogen dioxide, the other from the perchromic or per- 
manganic acid. These two atoms unite to form a molecule of 
oxygen 00. This would represent oxygen in the free state, 
and occupy two volumes. It would be a true combination, and 
we here encounter for the first time the important notion that 
the atoms of certain elements are not isolated when in the fi'ee 
state, but combined in pairs, each pair being held together by 
chemical force. Free oxygen would then be oxygen oxide, a 
combination of two atoms of oxygen, both together forming 
a molecule, and occupying two volumes like the molecule of 
water. 

1 molecule of water .... H-O-H = 2 volumes. 
1 molecule of oxygen . . . 0=0 = 2 volumes. 

While the molecular structure of free oxygen or oxygen 
oxide corresponds in a measure to that of hydrogen oxide or 
water, there exists a peroxide of oxygen which corresponds in 
a measure to hydrogen peroxide ; it is ozone. 

Hydrogen dioxide H-O-O-H 

Oxygen dioxide (ozone) Q^ | 



98 



ELEMENTS OF MODERN CHEMISTRY. 



SULPHUR. 

Vapor density compared to air 2.22 

Vapor density compared to hydrogen .... 32. 
Atomic weight S = 31.83 

Sulphur has been known from the greatest antiquity. It 
exists in combination in a large number of sulphides, among 
which are those of iron and copper (pyrites), of lead (galena), 
zinc (blende), mercury, etc. In certain volcanic countries it is 
found on the surface of the earth in the native state. Sicily and 
Iceland contain large deposits in the neighborhood of extinct 
volcanoes (solfatares). In order to separate it from the earthy 
matters which accompany it, the ore is piled symmetrically in 
hemispherical kilns about 10 metres in diameter built on the 
side of a hill (Fig. 31) ; air-channels are left through the 




Fig. 31. 



mass, and the whole is covered with a layer of earth or burnt- 
out ore. The sulphur is then ignited at the bottom, and the 
heat produced by the combustion of a portion of the sulphur 
causes that remaining in the mass to melt. The liquid sulphur 
runs out at the bottom of the kiln, and solidifies in masses or 
is cast into moulds. 

Crude sulphur is thus obtained. It is purified by distillation 
from the foreign matters which it retains. This refining process 
is conducted in an apparatus represented in Fig. 32. 



SULPHUR. 



99 



A horizontal cast-iron cylinder, A, receives the melted sul- 
phur from the vessel C, which is heated by the waste gases 
Prom the furnace, and which serves as a reservoir. The sulphur 
v^apor enters a large masonry chamber, B, the floor of which is 
slightly inclined in order that the condensed liquid sulphur may 
flow towards a tap, H, which can be opened as is necessary. A 
damper, R, that can be regulated by an articulated wire, per- 
mits the closing and opening of the mouth of the cylinder. 
The vault of the chamber is provided with a safety-valve, K, 
which allows of the escape of the expanded air. 

At the commencement of the operation, when the walls of 
the chamber are cold, the sulphur condenses in the form of a 
fine powder, which is known as flowers of suljplim\ But when 
the walls of the chamber become heated above the melting- 
point of sulphur, the vapor condenses into a liquid, and on 
opening the tap at H, it is drawn off into a vessel, E, from 
which it is distributed into slightly conical or cylindrical moulds, 
where it solidifies. Boll sulphur is thus obtained. 




Physical Properties. — Sulphur is a lemon-yellow solid. It 
is tasteless, odorless, and brittle ; it is a non-conductor of heat 



100 ELEMENTS OF MODERN CHEMISTRY. 

and electricity. A stick of sulphur pressed in the hand or 
plunged into warm water produces a crackling sound, and 
finally breaks into pieces ; this is due to the unequal expan- 
sion from the circumference to the centre of the non-conduct- 
ing mass of sulphur, the crystalline particles of which are but 
slightly held together by cohesion. 

The density of sulphur is about 2.03. At 111.5° it melts 
into a brownish-yellow, transparent liquid. If this liquid be 
■allowed to cool slowly until a crust forms upon the surface, 
and the crust be pierced and the part still remaining liquid be 
decanted, after removing the crust the vessel is found lined 
with long, transparent, flexible needles of a brownish-yellow 
color. These crystals are monoclinic prisms having a den- 
sity of 1.98. This is not the only crystalline form assumed 
by sulphur. If a solution of sulphur in carbon disulphide be 
allowed to evaporate spontaneously, orthorhombic pyramids are 
deposited having a density of 2.05. This form is also that of 
native sulphur. 

Sulphur crystallizes, then, in two distinct crystalline systems. 
It is dimorphous. It is a curious fact that the prisms formed 
by way of fusion do not long retain their transparency and 
their flexibility. At ordinary temperatures, they soon become 
opaque and brittle, owing to their transformation into micro- 
scopic orthorhombic octahedra. 

Conversely, the transparent octahedral crystals become 
opaque when maintained for some time at a temperature of 
111° ; they are then transformed into a multitude of little crys- 
tals of prismatic sulphur. The two crystalline modifications 
of sulphur are thus transformed into each other by varying 
the conditions. 

Sulphur melted in a sealed tube will remain liquid for a 
long time at temperatures below its ordinary point of solidifi- 
cation ; it is then said to be in a state of superfusion. When 
it finally solidifies, it crystallizes in voluminous octahedra 
having the form of crystallized native sulphur. 

There are other and amorphous modifications of sulphur. 

Experiment. — If sulphur be melted in a flask, and the tem- 
perature be gradually raised above its point of fusion, it assumes 
a thick consistence and a dark color. At 220° it has a brown- 
red color and is very thick. Above 260° it again becomes 
fluid ; if while in this state it be poured into cold water, it is 
converted into a soft, transparent, brownish-yellow, and elastic 



SULPHUR. 101 

mass. It has become amorphous, and is now soft sulphur. 
When abandoned to itself for several days, it hardens, becomes 
opaque, and reassumes the properties of ordinary sulphur. 
This change takes place immediately if the soft sulphur be 
heated to 90 or 95° ; is then accompanied by a sensible disen- 
gagement of heat (Regnault). 

There are two modifications of soft sulphur. If it be treated 
with carbon disulphide, a part of it is dissolved, and a residue 
remains. The soluble part constitutes soluble soft sulphur ; 
the residue is insoluble soft sulphur (Ch. Sainte-Claire Deville). 
In recently-sublimed flowers of sulphur the sulphur exists in 
the amorphous condition. 

Sulphur boils at 448° ; its vapor is yellowish brown. The 
density of the vapor at 470° is nearly 8, but it gradually 
diminishes when the temperature is raised, until it becomes 
constant at about 1000°. Between 1000° and 1700° it is 
2.22 compared to air, or 32 compared to hydrogen. Hence 
the molecular weight of sulphur is 2 X 32 = 64. This 
corresponds to the formula S^ 

At temperatures below 1000° sulphur does not appear to 
assume the true gaseous condition : its molecules then con- 
sist of more than two atoms. It was formerly believed that 
just above the boiling-point the sulphur molecules consist of 
six atoms, the vapor density being approximately 96. This 
value, however, does not remain constant. In solutions the 
molecular weight of sulphur has been found to correspond to 
the formula S^. 

Sulphur is insoluble in water, but very slightly soluble in 
alcohol, a little more soluble in ether and benzene. Its best 
solvent is carbon disulphide. 

Chemical Properties. — Sulphur possesses energetic affini- 
ties. It combines directly with a great number of the other 
elements. It is well known that it is combustible, burning 
with a blue flame. Its combustion in air or oxygen produces 
sulphur dioxide. 

Sulphur combines directly with chlorine, bromine, iodine, 
phosphorus, arsenic, and carbon, and with very many of the 
metals. Iron and copper burn in the vapor of sulphur. The 
sulphides thus formed generally possess the atomic constitution 
of the corresponding oxides. Thus, the compound of sulphur 
and carbon, carbon disulphide, is analogous to carbonic acid 
gas. This analogy is maintained between a great number of 

9* 



102 



ELEMENTS OF MODERN CHEMISTRY. 



oxygen and sulphur compounds, as will be seen by the follow- 



ing examples 



H20 water. 

H^S hydrogen sulphide. 

KOH potassium hydroxide. 

KSH potassium sulphydrate. 

C02 carbon dioxide. 

C& carbon disulphide. 



K^O potassium monoxide. 
K^S potassium monosulphide. 
BaO barium monoxide. 
BaS barium monosulphide. 
K^CO^ potassium carbonate. 
K2CS3 potassium sulphocarbonate. 



SULPHYDRIC ACID, OK HYDROaEN SULPHIDE. 

Density compared to air 1.192 

Density compared to hydrogen 17. 

Molecular weight H2S = 33.83 

This gas, known also as sulphuretted hydrogen, was discov- 
ered by Meyer and Rouelle, and studied 
by Scheele, in 1777, and by BerthoUet. 

Preparation. — Hydrogen sulphide is 
usually prepared in the laboratory by the 

A liSilfeliii reaction of dilute sulphuric acid and fer- 

rous sulphide, as indicated in the follow- 
ing equation : 

FeS + H^SO* = FeSO* -f H^S 

Ferrous Sulphuric Ferrous 

sulphide. acid. sulphate. 

The apparatus used for the preparation 
of hydrogen may be employed. As hy- 
drogen sulphide is very largely used as 
a reagent, many forms of self-regulating 
apparatus have been devised by which 
the gas may be obtained as required. 
One of the most convenient of these is 
due to Norblad, and is represented in 
Fig. 33. Ferrous sulphide is introduced 
into the bulb B, to which another bulb, 
C, is adapted by a well ground joint. 
The only passage from ^ to (7 is by 
means of a groove in one side of this 
joint in B and a small hole in C which 
may be brought opposite the groove. 
The hole opens into a tube which rises 
in C and is then directed downward, so that gas coming from 
B must pass through a little water contained in the bulb 




Fig. 33. 



HYDROGEN SULPHIDE. 103 

and be thus washed. Dilute sulphuric acid is poured into the 
reservoir A, the stop-cock D being closed. As soon as the 
liquid comes in contact with the ferrous sulphide, hydrogen 
sulphide is disengaged and passes out by the delivery-tube F. 
On closing the passage from B to C hj rotating C so that the 
opening in the ground joint is not opposite the groove in B, 
the accumulation of gas forces the acid liquid back into the 
reservoir A, and the reaction ceases as soon as the acid is no 
longer in contact with the ferrous sulphide. The stop-cock D 
serves to draw off the liquid when the acid becomes exhausted. 
A much purer hydrogen sulphide may be prepared by heat- 
ing antimony trisulphide with hydrochloric acid. The reaction 
takes place according to the following equation, the antimony 
trichloride remaining in solution : 

Sb^S^ + 6HC1 = 2SbCP -f SH^S 

Antimony trisulphide. Hydrochloric acid. Antimony trichloride. 

It has been recently recommended to employ aluminium sul- 
phide, APS^, when the gas is wanted perfectly pure. The re- 
action which takes place is exactly analogous to the preceding. 

Hydrogen sulphide may be collected over warm water or by 
dry downward displacement. 

Physical Properties. — Hydrogen sulphide is a colorless gas. 
It has a penetrating odor of putrid eggs. Under a pressure of 
17 atmospheres, it condenses to a transparent, strongly refract- 
ing liquid, having a density of about 0.91. At — 85.5° this 
liquid solidifies to a white crystalline mass (Faraday). Hydro- 
gen sulphide is soluble in water. At 0°, one volume of water 
dissolves 4.37 volumes; at 10°, 3.58 volumes; and at 20°, 
2.90 volumes. 

Composition. — 2 volumes of hydrogen sulphide contain 2 
volumes of hydrogen and 1 volume of sulphur vapor. 

If a given volume of this gas be introduced into a bent tube 
over mercury (Fig. 44), and a morsel of tin be then introduced 
and heated for about twenty minutes, the hydrogen sulphide is 
decomposed ; the sulphur combines with the tin, and the hy- 
drogen is set free. After cooling, the latter gas occupies a 
volume exactly equal to that of the hydrogen sulphide at first 
contained. 

The density of hydrogen sulphide = 17 

hence its molecular weight = 34 

subtracting from this the weight of one molecule of 

hydrogen = 2 

we obtain the weight of one atom of sulphur . . . = 32 



104 ELEMENTS OF MODERN CHEMISTRY. 

It is hence concluded that one molecule of hydrogen sulphide 
contains one atom of sulphur to two atoms of hydrogen. 

It is also seen that hydrogen sulphide has exactly the same 
chemical constitution as vapor of water. 

H^O = 2 volumes or one molecule of vapor of water. 

H^S = 2 volumes or one molecule of hydrogen sulphide. 

The analogy between sulphur and oxygen is here manifested 
in a striking manner. One atom of each of these elements 
requires two atoms of hydrogen. This is expressed by saying 
that both oxygen and sulphur are diatomic elements. 

Chemical Properties. — Hydrogen sulphide is combustible, 
burning with a bluish flame. The products of its complete 
combustion are water and sulphur dioxide. When mixed 
with one and a half times its volume of oxygen, it explodes on 
the application of a flame or the passage of an electric spark. 

2H2S + 30^ = 280^ + 2W0 

Two volumes. Three volumes. Two volumes. Two volumes. 

When the supply of oxygen is insufficient, the combustion 
is incomplete and sulphur is deposited. 

In the presence of water, oxidation takes place slowly at 
ordinary temperatures, occasioning a deposit of sulphur. In 
contact with porous matters and oxygen the oxidation goes 
further, sulphuric acid being formed. 

Hydrogen sulphide has a feeble acid reaction ; it changes 
blue litmus to a wine-red color. When it reacts with potassium 
hydrate, water and potassium sulphydrate are formed. 

i}s + i}o = i}s + l}o 

Hydrogen sulphide. Potassium hydrate. Potassium sulphydrate. 

Chlorine, bromine, and iodine decompose hydrogen sulphide, 
combining with its hydrogen. When these bodies are dry, the 
action is energetic, and the sulphur combines with the excess 
of the element employed. If water be present, the sulphur 
is set at liberty. 

Bodies rich in oxygen readily decompose hydrogen sulphide. 

Experiments. — 1. If a few drops of the strongest nitric acid 
be poured into a jar filled with hydrogen sulphide, the gas is 
instantly inflamed. The nitric acid gives up oxygen, water is 
formed, sulphur is set free, and abundant red fumes appear at 
the same time. 



HYDROGEN PERSULPHIDB. 105 

2. If four volumes of hydrogen sulphide be mixed with two 

volumes of sulphur dioxide over the mercury-trough, a deposit 
of sulphur is at once formed. 



2H^S + SO^ =: 


2ffO 


+ 3S 


Hydrogen sulphide. Sulphur dioxide. 


Water. 


Sulphur. 


(4 volumes.) (2 volumes.) 







Hydrogen sulphide decomposes a great number of metallic 
solutions, forming insoluble sulphides, which are precipitated. 

The color, solubility in acids and alkalies, and other charac- 
teristics of the precipitates thus formed render hydrogen sul- 
phide an almost indispensable reagent in analysis. 

Experiments. — 1. If hydrogen sulphide be passed into a 
solution of blue vitriol or cupric sulphate, a brownish black 
precipitate of cupric sulphide is formed. The reaction is 
expressed by the following equation : 

CuSO* -f- H^S = CuS + H^SO* 

Cupric sulphate. Cupric sulphide. Sulphuric acid. 

2. By an analogous reaction, a solution of plumbic acetate, 
or a paper impregnated with that salt, is at once blackened by 
the presence of hydrogen sulphide. 

In the same manner hydrogen sulphide throws down white 
zinc sulphide from alkaline solutions of zinc salts, the pre- 
cipitate being redissolved by acids. In acid solutions of anti- 
mony it forms an orange precipitate of antimony trisulphide 
insoluble in ammonia, while arsenic is precipitated as yellow 
arsenic trisulphide, soluble in ammonia, from acid solutions 
of arsenic. 

Hydrogen sulphide acts as a poison when inhaled in large 
quantities or for any length of time. 

HYDROGEN PERSULPHIDE. 

H2S5 (probably). 

This compound is prepared by pouring, drop by drop, a 
solution of calcium disulphide into dilute hydrochloric acid. 

4CaS2 -f 8HC1 =^ 4CaCP + SH^S + H^S^ 

Calcium disulphide. Hydrochloric acid. Calcium chloride. Hydrogen persulphide. 

Hydrogen persulphide is formed and collects at the bottom of 
the vessel in the form of a yellowish oil, having a disagreeable, 
irritating odor. 



106 ELEMENTS OP MODERN CHEMISTRY. 

Under a pressure of five millimetres it may be distilled at 
about 60°, and is then colorless. When perfectly dry it is 
stable if kept in the dark, but in the light, or if moisture be 
present, it soon decomposes into hydrogen sulphide and sul- 
phur. This decomposition is also brought about by presence 
of the bodies that react with either hydrogen sulphide or 
sulphur. 

OXYGEN ACIDS OF SULPHUR. 

1. Sulphur forms four compounds with oxygen : 

Sulphur sesquioxide S^O^ 
Sulphur dioxide SO^ 
Sulphur trioxide SO^ 
Persulphuric oxide S^O^ 

2. By combining with a molecule of water, the last three 
are converted into the corresponding acids. 

SO^ + H^O = H=^SO-^ sulphurous acid. 
SO^ + H^O = H^SO* sulphuric acid. 
S^O^ + H^O = 2HS0* persulphuric acid. 

3. There are two other important acids of sulphur, thio- 
sulphuric and hyposulphuric acids. The former may be con- 
sidered as sulphuric acid in which 1 atom of oxygen is replaced 
by an atom of sulphur. 

H=^S0* sulphuric acid. 

H\S0^)S thiosulphuric (formerly called hyposulphurous) 
acid. 

Hyposulphuric acid may be considered as resulting from the 
addition of sulphurous oxide to sulphuric acid. 

SO^ + H^SO* =^ H'^S^O^ hyposulphuric acid. 

4. These are not the only known sulphur acids. 
Hyposulphuric acid, which is called also dithionic acid, is 

the first of a series of acids, each of which contains 2 atoms of 
hydrogen and 6 atoms of oxygen, the number of sulphur atoms 
regularly increasing. This series is called the thionic series. 
The following is the nomenclature and composition of the 
acids : 

H^S^O® dithionic or hyposulphuric acid. 

H'S'O^ trithionic acid. 

H^S*0^ tetrathionic acid. 

H^S^O^ pentathionic acid. 



SULPHUR DIOXIDE. 107 

5. Schiitzenberger made known a new sulphur acid, which 
he named hydrosulphurous acid, and which is formed by the 
action of zinc upon sulphurous acid, as will be described farther 
on. The composition of this acid, which is properly named 
hyposulphurous, is represented by the formula 
H^SO^ or H^S^O^ 
There is an interesting relation between this acid and sul- 
phurous and sulphuric acids. 

H^SO^ hyposulphurous acid. 
H^SO' sulphurous acid. 
H'^SO* sulphuric acid. 
Sulphur sesquioxide, S^O^ appears to be a green solid, 
obtained by the action of sulphur on sulphur trioxide in the 
cold. It is very unstable, decomposing readily into sulphur and 
sulphur dioxide. 

SULPHUR DIOXIDE. 

Density compared to air 2.234 

Density compared to hydrogen 31.795 

Molecular weight S02 = 63.59 

Sulphur dioxide or sulphurous acid gas may be prepared 
by decomposing sulphuric acid with copper. The metal in 
small clippings and the acid are introduced into a flask fitted 




with a delivery-tube (Fig. 34) ; heat is applied and the gas 
collected over the mercury- trough. The reaction which takes 
place is expressed by the following equation : 

Cu + 2H2SO* = CuSO* + 2H^0 -j- SO'* 

Copper. Sulphuric acid. Cupric sulphate. 



108 ELEMENTS OF MODERN CHEMISTRY. 

A solution of sulphurous acid in water is often needed in 
the laboratory. It may be conveniently prepared by reducing 
sulphuric acid by charcoal ; the products of the reaction are 
water, and sulphurous and carbonic acid gases. 

2H2SO* + C = 2H^0 + 2S0' + CO^ 

Sulphuric acid. Carbon dioxide. 

The mixed gas is passed through a series of bottles contain- 
ing water, which dissolves the sulphur dioxide, but takes up 
only an insignificant quantity of the carbon dioxide. 

Physical Properties. — Sulphur dioxide is a colorless gas 
having a pungent, suffocating odor. It is readily liquefied by 
being led into a vessel surrounded by a mixture of ice and salt. 
It condenses at ordinary temperatures, under a pressure of 
about two atmospheres. The liquid has a density of 1.45; it 
boils at — 8°, and produces great cold by its evaporation ; on 
this account it is used for the manufacture of ice, and in other 
cases where intense cold is required. — 73° may be obtained 
by the evaporation of liquid sulphurous acid aided by double- 
acting pumps (Kaoul Pictet). 

Water at 0° dissolves 79.9 times its volume of sulphur di- 
oxide, and only 39.4 volumes at 20°. 

Experiments. — 1. If a small quantity of mercury contained 
in a porcelain capsule be covered with a deep layer of liquid 
sulphur dioxide, and the evaporation of the latter be favored 
by directing a rapid current of air over its surface, the mercury 
is frozen into a solid button. 

2. When liquid sulphurous acid is poured into not too great 
a quantity of water, a part of it is dissolved, but the excess 
absorbs heat from the mass of liquid, volatilizes suddenly, and 
the water is frozen. 

Chemical Properties. — Sulphur dioxide is not decomposed 
by heat. It is incombustible, and extinguishes burning bodies. 

Its most striking property is its affinity for oxygen. If a 
mixture of two volumes of sulphur dioxide and one volume 
of oxygen be passed through a tube containing slightly 
heated spongy platinum, the two gases combine, forming 
sulphur trioxide (Kuhlmann). 

A solution of sulphur dioxide in water slowly absorbs 
oxygen, and is converted into sulphuric acid. It may be 
admitted that the aqueous solution contains the veritable 
sulphurous acid. 



SULPHUR DIOXIDE. 109 

Sulphurous acid. Sulphuric acid. 

Sulphurous acid reduces a great number of oxidized bodies. 
At ordinary temperatures it takes the oxygen from iodic acid, 
setting free the iodine ; but the latter disappears on the addi- 
tion of an excess of sulphurous acid, sulphuric and hydriodic 
acids being formed. 

H^SO^ + H^O + r = H^SO* + 2HI 

It decolorizes the purple solution of potassium permanganate, 
forming manganese sulphate and potassium sulphate. It con- 
verts arsenic acid into arsenious acid. It combines directly 
with lead dioxide, forming lead sulphate. 

PbO^ + SO^ = PbSO* 

Lead dioxide. Lead sulphate. 

Chlorine will unite directly with sulphur dioxide. If a 
mixture of equal volumes of chlorine and sulphur dioxide 
be exposed to sunlight, the two gases combine, forming a liquid 
having a suffocating odor. It is sulpliuryl chloride. Its den- 
sity is 1.66, and its boiling-point is 77°. It may be regarded 
as sulphur trioxide in which one atom of oxygen is replaced 
by two atoms of chlorine. 

SO^ = (S0^)"0 sulphuryl oxide or sulphuric oxide. 
SO^CP = (SO')"CP sulphuryl chloride. 

In these reactions in which the sulphur dioxide combines 
directly with either one atom of oxygen or two atoms of chlorine, 
it plays the part of an element ; it is a compound radical, and 
this radical is diatomic, because it unites with two atoms of the 
monatomic element chlorine, or with one atom of the diatomic 
element oxygen, which is equivalent to two atoms of chlorine. 

In the formulae given, the diatomicity is expressed by the 
accents ". 

Sulphurous acid bleaches various vegetable and animal mat- 
ters. A bouquet of violets or a rose is bleached in a few minutes 
by a solution of sulphur dioxide. This property renders sul- 
phur dioxide a valuable bleaching agent. It is extensively 
employed also as a disinfectant, and for arresting or retarding 
processes of putrefaction and fermentation. 



10 



110 ELEMENTS OP MODERN CHEMISTRY. 

HYPOSULPHUROUS (HYDROSULPHUROUS) ACID. 

H2S02 
While sulphurous acid reduces a number of bodies, it is in its 
turn reduced by the action of zinc upon its aqueous solution. A 
yellow liquid is thus obtained which energetically bleaches indigo 
and litmus solutions (Schonbein). Schiitzenberger has shown 
that the liquid gifted with these properties contains the zinc salt 
of a new acid, which is properly named hyposulphurous. This 
acid is formed by the combination of hydrogen with sulphur 
dioxide. The reaction is expressed by the following equations : 
H^SO^ + Zn = ZnSO^ + H^ 

Sulphurous acid. Zinc. Zinc sulphite. 

SO^ -{- W = W^O' 

Sulphur dioxide. Hyposulphurous acid. 

When this liquid is treated with very dilute sulphuric acid, 
it gives a liquor of a dark orange-yellow color, having ener- 
getic bleaching powers. It then contains hyposulphurous 
acid. It soon becomes clouded and deposits sulphur. This 
acid is not stable, but its acid sodium salt is more so ; the latter 
has the composition NaHSO^. It readily absorbs oxygen from 
the air, being converted into sodium acid sulphite. 
NaHSO^ + = NaHSO^ 

This oxidation is also brought about by the presence of cer- 
tain metallic salts, such as those of copper, mercury, and lead. 
In this case the metal is reduced and precipitated, and the 
hyposulphite is decomposed, yielding sulphur dioxide. 

NaHSO^ -f CuSO* = NaHSO* + SO^ + Cu 

Sodium hyposulphite. Cupric sulphate. Sodium acid sulphate. 

Sodium acid hyposulphite may be obtained by the electrol- 
ysis of a solution of sodium acid sulphite. In this case the 
hydrogen, which would otherwise be disengaged at the negative 
pole, accomplishes the reduction. 

NaHSO^^ + IP = NaHSO^ + H=^0 

SULPHUR TRIOXIDE, OR SULPHURIC OXIDE. 

(SULPHURIC ANHYDRIDE.) 

Vapor density compared to hydrogen .... 39.736 
Molecular weight S0» = 79.47 

Sulphur trioxide is formed by the union of oxygen with 
sulphur dioxide in the presence of finely-divided platinum. 



SULPHURIC ACID. Ill 

It has long been prepared by gently heating fuming sulphuric 
acid in a retort ; vapors are given off which, when condensed 
in a receiver surrounded by a freezing mixture, solidify into a 
white mass, having a fibrous appearance and a silky lustre. 
According to Weber, the silk-like solid is an impure trioxide 
containing small quantities of 3S0MI'''S0*. It is purified by 
repeated meltings at a moderate temperature, decanting the 
liquid from the still solid portion until all melts at the same 
temperature. 

Thus prepared, sulphur trioxide is a mobile liquid which 
boils at 46.2°, and upon slow cooling solidifies in long prisms 
which melt at 14.8°. At ordinary temperatures it produces 
white fumes in the air by condensing the atmospheric moisture. 
Its most striking property is its afl&nity for water ; when thrown 
into that liquid, it becomes hydrated with such energy that a 
portion of the water is suddenly vaporized, and a hissing noise 
is produced similar to that heard on plunging a red-hot iron 
into water. 

SULPHUEIC ACID. 

Molecular weight JJ^^go^ = 97.36 

This acid, which has been known for centuries, was formerly 
obtained by the distillation of ferrous sulphate. Now that 
enormous quantities of it are annually consumed in the manu- 
facture of many important products, it is universally obtained 
by what is known as the lead chamber process. This consists 
in conducting into leaden chambers a mixture of sulphur 
dioxide, oxides of nitrogen, and steam : oxidation takes place, 
and the sulphur dioxide is converted into sulphuric acid. 

SO^ + NO''' + H^'O := H^SO* + NO 

Nitrogen peroxide. Nitric oxide. 

^ The nitric oxide resulting from this reaction then combines 
with the oxygen of the air contained in the chamber, and is 
reconverted into nitrogen peroxide. 

2N0 + O^ = 2N0^ 

The latter again reacts with the sulphur dioxide and 
steam which continually arrive in the chamber, and more 
sulphuric acid results. It is a continuous operation, which 
theoretically leaves no residue, and permits of the conversion 
of an indefinite amount of sulphur dioxide into sulphuric acid. 



112 



ELEMENTS OF MODERN CHEMISTRY. 



It is really the oxygen of the air, continually absorbed and 
given up by the nitric oxide, which effects the oxidation of 
the sulphur dioxide ; the nitrogen peroxide is the direct agent, 
and the nitric oxide is intermediate, for it is the vehicle for 
the transfer of the oxygen * 

The reactions may be well exhibited by the aid of the appa- 
ratus shown in Fig. 35, in which sulphur dioxide from the 

flask B and nitric 
oxide prepared by 
the action of nitric 
acid on copper in the 
generating bottle C 
are conducted into a 
large globe, A, con- 
taining a little water. 
The cork of the 
globe is also pro- 
vided with two bent 
tubes, through one 
of which air or oxy- 
FiG. 35. g^i^ ^^y be blown 

in, while the other 
serves as an exit for the gases. The color of the gases in the 
globe indicates the phases of the reaction, the red vapors produced 
by the action of air on the nitric oxide being rapidly reduced 
to colorless NO by contact with the sulphur dioxide. During 
the reaction the walls of the globe become lined with long white 
crystals, which are a compound of sulphurous acid and nitrogen 
peroxide; on agitating the globe so that they come in contact 
with water, they are at once decomposed into sulphuric acid and 
red vapors. They are known as the leaden chamber crystals. 

Fig. 36 represents a section of a series of leaden chambers 
for the manufacture of sulphuric acid. 

Sulphur or pyrite is burned in furnaces, AA, and the heat 
generated is employed to boil the water contained in the boilers 




* According to Lunge the formation of sulphuric acid in the lead- chamber 
process is more correctly represented by the following equations : 
2S02 + NO + N02 + 02 + H20 = 2H(N0)S0* 
The product, nitrosyl suljihuric acid, is then converted into sulphuric 
acid by an excess of water. 

2H(N0)S0* + H20 = 2H2S04 + N0-+ N02 



SULPHURIC ACID. 



113 




10* 



114 ELEMENTS OF MODERN CHEMISTRY. 

above the flame, the steam being distributed to the chambers 
by the pipes c d. The sulphurous oxide, together with a 
great excess of air, passes through the pipes BB into a leaden 
drum, C. A thin layer of sulphuric acid charged with nitrous 
products trickles over the inclined shelves in the drum. The 
gases pass first into the chamber C, then into D, where they 
meet with nitric acid, which falls in thin layers over a double 
cascade, EE, in such a manner as to present a large surface for 
the action of the sulphurous oxide. The sulphuric acid which 
is formed in this chamber is charged with nitrous products ; it 
is therefore allowed to flow by the inclined tube F into the 
chamber C, where it encounters an excess of sulphurous oxide, 
and which is called the denitrifier. The sulphurous oxide, the 
excess of air, and the nitrogen peroxide pass from D into the 
large chamber HH, into which steam is projected by several 
jets. Here the larger portion of the sulphuric acid is pro- 
duced, and the reaction is completed in another chamber. In 
the engraving the last two chambers are not fully represented. 
The gases from the last chamber enter a refrigerator, in which 
the condensation takes place ; they are lastly conducted into a 
leaden column, B, filled with coke which is kept saturated 
with sulphuric acid by a thin stream from the reservoir 0. 
This acid completely absorbs the nitric oxide, and descends 
by the tube ha into the reservoir i, situated near the furnace. 
As soon as this reservoir is full, the stop-cock r is closed, and 
/ is opened ; the pressure of the steam then forces the acid 
up into the reservoir ^, which feeds the first drum. The gas 
which escapes from the last column, which is known as Gay- 
Lussac's tower, consists of nitrogen charged with an insignifi- 
cant quantity of nitrous vapors. 

The acid which is drawn from the chambers is not suffi- 
ciently concentrated, having a density of only about 1.5. It 
is first evaporated in leaden vessels until it becomes strong 
enough to act upon the lead, and the concentration is then fin- 
ished in large platinum retorts. The excess of water is thus 
driven out. The concentrated acid possesses a density of 
1.842. 

In many manufactories pyrites is burned instead of sulphur. 
Sulphurous oxide is produced, and a residue of ferric oxide 
remains. 

Purification of Sulphuric Acid. — The sulphuric acid of 
commerce contains impurities. It holds. in solution a small 



SULPHURIC ACID. 115 

quantity of lead sulphate, formed in the evaporating basins ; it 
is often charged with nitrous products, and sometimes with ar- 
senic acid, when the sulphurous oxide employed in its prepa- 
ration has been obtained by the combustion of arsenical pyrites. 
It may be freed from these impurities by distillation. The 
nitrous products are first disengaged, and are found in the first 
portions of the distillate, which must be rejected. Pure sul- 
phuric acid then passes ; the lead sulphate and arsenic acid 
remain in the retort with the last portions of the acid, which 
must not be distilled. 

The operation may be conducted in a glass retort connected 
with a cooled receiver. The retort should be heated laterally 
by an annular flame so that explosive evolution of vapor may 
be avoided, and it is well to introduce some platinum wires with 
the acid, and to cover the retort with a sheet-iron hood. 

Constitution of Sulphuric Acid. — Since oxygen combines 
directly with sulphur dioxide to form sulphuric oxide, the 
latter may be regarded as sulphuryl oxide, SO^O. 

Sulphuric acid is the hydrate of this oxide. 

SO^' + H^O = H^SO* 

The following experiment indicates the relations which exist 
between the elements composing this hydrate. 

If sulphuryl chloride be poured into water, it disappears, 
sulphuric acid and hydrochloric acid being formed. 

SO^jcl + ioH = SO^lol + 2™ 

Sulphuryl 2 molecules Sulphuric 2 molecules 

chloride. of water. acid. hydrochloric acid. 

Sulphuric acid is thus formed by the decomposition of 2 
molecules of water, of which 2 atoms of hydrogen have been 
removed by 2 atoms of chlorine, and replaced by the group 
SO^. It may then be truly said that sulphuric acid is derived 
from two molecules of water by the substitution of the diatomic 
radical (SO^)" for two monatomic atoms of hydrogen. 

H.OH rQir\'2\rf j OH 

H.OH ^^^^ I OH 

2 molecules of water. Sulphuric acid. 

If the composition of sulphuric acid be compared to that 
of sulphuryl chloride, from which it may be formed, it will be 



116 ELEMENTS OF MODERN CHEMISTRY. 

seen that both compounds contain the same nucleus or radical 
SO^ and that instead of the two atoms of chlorine of the 
chloride, the acid contains two groups OH. The group OH 
is a residue, as it were, which represents a molecule of water 
minus one atom of hydrogen, and which is called hydroxyl. 
It is a monatomic group, and sulphuric acid is formed by the 
saturation of the affinity of the diatomic radical sulphuryl by 
two monatomic groups hydroxyl, which replace the two atoms 
of chlorine of sulphuryl chloride. Williamson has described 
an intermediate compound in which the radical sulphuryl is 
combined with one atom of chlorine and one OH group. 

SO'{C} SO^jCl^ SO^jOH 

Sulphuryl chloride. Sulphuryl chlorohyJrate. Sulphuric acid. 

Physical Properties. — Sulphuric acid is a colorless oily 
liquid ; its density at 12° is 1.842 (Marignac). Its boiling-point 
is 325°, and it solidifies at — 34°. If it be crystallized several 
times at a low temperature, and the part remaining liquid be 
decanted off each time, the melting-point is gradually raised to 
-|-10.5°, where it remains stationary. According to Marignac, 
the acid which solidifies and fuses at -|-10.5° constitutes the 
true monohydrated acid, H'SO*. At a temperature about 40° 
it emits some fumes, and between this point and 290° it disen- 
gages a small quantity of vapor of sulphuric oxide. At 290° 
it begins to boil, but its boiling-point soon rises to 338°, where 
it remains. Such are, according to Marignac, the properties of 
monohydrated sulphuric acid. According to this chemist, the 
acid purified by simple distillation, and boiling at 325°, still 
contains a small amount of water. 

Chemical Properties. — When exposed to a red heat, sul- 
phuric acid decomposes into sulphur dioxide, oxygen, and 
water. 

W80' = SO^ + + H^O 

Many bodies having an affinity for oxygen reduce sulphuric 
acid by the aid of heat. Thus sulphur effects the reduction, 
being at the same time oxidized to sulphur dioxide. 

2ffS0* + S == 3S0' + 2H^0 
We have already studied the action of charcoal and copper 
upon sulphuric acid when boiled with that liquid, and we have 
seen that zinc and iron decompose the dilute acid with evolu- 
tion of hydrogen and formation of a sulphate. 



SULPHURIC ACID. 117 

Sulphuric acid has a strong affinity for water. When four 
parts of sulphuric acid are quickly mixed with one part of 
water, the temperature rises to above 100°. If the experiment 
be made with large quantities, it is not without danger, and re- 
quires prudence lest part of the acid be projected from the vessel. 

Experiments. — If four parts of sulphuric acid be quickly 
added to one part of snow, the latter is immediately liquefied 
and a notable elevation of temperature takes place ; for the 
energy of the combination of the sulphuric acid with the water 
is so great that the heat produced by the union is greater than 
that consumed in the liquefaction of the ice. 

But if four parts of snow be mixed with one part of sul- 
phuric acid, the result is the reverse ; there is a lowering of 
temperature. 

The affinity of sulphuric acid for water is manifested in a 
number of reactions. In the following it is sufficiently power- 
ful to cause the formation of the water it requires : 

If a morsel of sugar be moistened with sulphuric acid, it 
becomes blackened and carbonized in a few minutes. The sugar 
contains no water already formed, but independently of carbon 
it contains hydrogen and oxygen in the proportions necessary 
to form water, so that the latter compound is produced by the 
influence of the sulphuric acid, and a carbonaceous matter 
remains. 

This water which is absorbed by sulphuric acid with so much 
energy, combines with the acid in a manner analogous to that 
in which water of crystallization combines with certain salts. 
Indeed, if sulphuric acid to which 18.3 per cent, of water has 
been added be exposed to a temperature of 0°, large prismatic 
crystals are formed, which remain solid even at a temperature 
of -f7° or -]-8°. The composition of these crystals is ex- 
pressed by the formula H^SO*,H^O. They constitute a dihy- 
drated acid, for they result from the union of two molecules 
of water with one molecule of sulphuric oxide. 

Concentrated stilphuric acid will absorb red nitrous vapors 
(see page 165), forming colorless crystals that are often de- 
posited in the leaden chambers. The compound is nitrosul- 
pJionic acid, or nitrosyl sulphuric acid. 

to}sO^ + No4*^ = NO.o}sO^ + HNO' 

Sulphuric acid. Bed vapors. Nitrosyl sulphuric Nitric acid. 

acid. 



118 ELEMENTS OF MODERN CHEMISTRY. 

Sulphuric acid is a dibasic acid ; that is, it contains two atoms 
of hydrogen that are replaceable by an equivalent quantity of 
metal. This substitution takes place when the acid is treated 
with a hydroxide, such as potassium hydroxide, or with an 
oxide, such as lead oxide. 

H^SO* + 2K0H = K^SO* + 2H='0 

Potassium hydroxide. Potassium sulphate. 

H^SO* + PbO = PbSO* + WO 

Lead oxide. Lead sulphate. 

' When saturated with potassium hydroxide, the sulphuric acid 
is converted into potassium sulphate, and, in the salt, two atoms 
of potassium replace the two atoms of hydrogen of the acid. 
In the case of the lead oxide, on the contrary, the reaction, 
which is only a double decomposition, takes place so that a 
single atom of lead replaces the two atoms of hydrogen. The 
metal lead is then said to be diatomic ; that is, one atom of 
lead is capable of replacing two atoms of a monatomic element 
such as hydrogen, and one atom of lead is equivalent to two 
atoms of potassium. 

Sulphuric acid may be detected by the following reactions, 
which are also applicable to the soluble sulphates. 

In solutions containing sulphuric acid or a sulphate, barium 
salts produce a white pulverulent precipitate, which is insolu- 
ble in either cold or hot nitric acid ; this precipitate is barium 
sulphate. When mixed with an excess of charcoal and heated 
to whiteness, it is converted into barium sulphide. 
BaSO* + 4C = 4C0 + BaS 

Barium sulphate. Carbon monoxide. Barium sulphide. 

The sulphide of barium disengages hydrogen sulphide when 
it is moistened with hydrochloric acid ; this gas may be recog- 
nized by its odor and by its blackening a paper impregnated 
with lead acetate. 

PYROSULPHURIC ACID. 

Fuming sulphuric acid, or Nordliausen acid, is a solution of 
sulphur trioxide in sulphuric acid, in which these bodies exist 
in combination as pyrosulphuric acid, H^S^O^ 

H'SO* 4- SO' =: H^S^O' =- 

S0'< 
OH 



HYPOSULPHUROUS ACID. 119 

This body is a colorless, fuming liquid, which, upon cooling, 
solidifies to a leafy mass which melts at 35°. When heated, 
it decomposes into sulphur trioxide and sulphuric acid. The 
commercial product is obtained either by dissolving sulphuric 
anhydride in sulphuric acid, or by distilling the ferric subsul- 
phate which results from the roasting of green vitriol. 

This subsulphate is calcined in stoneware retorts ; it gives 
off sulphuric oxide when it is perfectly dry. but as it is difficult 
to entirely free it from water of crystallization, the vapor of 
sulphuiic oxide is mixed with that of sulphui'ic acid, and the 
mixed vapors are condensed in cooled receivers. The residue 
of the distillation is ferric oxide, Fe^O^ Fuming sulphuric 
acid is used by dyers to dissolve indigo. 

THTOSULPHUKIC ACID. 

H2S(S03) 
This acid, called also hyposulphurous and sulphosulphuric 
acid, is not known in the free state. When sodium thiosulphate 
is treated with dilute sulphuric acid, the thiosulphuric acid set 
free is at once decomposed into sulphurous acid and sulphur. 
Na^s^o^ -^ H^SO* = Na^SO^ + H^SO^ + S 

Sodium thiosulphate. Sodium sulphate. 

Sodium thiosulphate is formed when sulphur is boiled with 
a solution of sodium sulphite. 

Na^SO^ -r S = Na^SCSO^) 

Sodium sulphite. Sodium thiosulphate. 

It is a very soluble salt, forming voluminous crystals. It is 
used in photography and in the manufacture of paper. 

HYPOSULPHURIO (DITHIOXIC) ACID. 

If faming sulphuric acid represent a combination of sul- 
phuric acid and sulphur trioxide. hyposulphuric acid can be 
regarded as resulting from the union of sulphuric acid with 
sulphur dioxide. 

SQIH'SO* pyrosulphuric acid, 
SO^.H-SO* hyposulphuric acid. 
Preparation.— Hyposulphuric acid is prepared by passing 
sulphur dioxide into water in which manganese dioxide is sus- 
pended. 2S0^ -f MnO^ = MnS^O^ 

ilanganese dioxide. Manganese hyposulphate. 



120 ELEMENTS OF MODERN CHEMISTRY. 

Manganese hyposulphate is thus formed, and this is con- 
verted into barium hyposulphate by a double decomposition 
with barium sulphide. The liquid is separated from the man- 
ganese sulphide by filtration, and exactly decomposed with 
dilute sulphuric acid. Barium sulphate is precipitated, and the 
hyposulphuric acid remains in solution. The liquid is then 
concentrated in vacuo. 

Properties. — Hyposulphuric acid is a very acid, syrupy 
liquid, having a density of 1.347. It is not stable ; when 
boiled it decomposes into sulphuric acid and sulphurous oxide. 



SULPHUR HEPTOXIDE AND PERSULPHURIC 
ACID. 

S^O^ and HSO* 

When a mixture of equal volumes of perfectly dry sulphur 
dioxide and oxygen is subjected to the silent electric dis- 
charge, sulphur heptoxide is formed, and part of the oxygen 
remains (Berthelot). 

4S0'^ + 40^^ = 2S^0^ + 0^ 

Sulphur heptoxide. 

Sulphur heptoxide is a viscous liquid which solidifies at 
O'', crystallizing sometimes in granules, sometimes in flexible 
needles. It is very unstable, and decomposes spontaneously, 
rapidly on heating, into sulphur trioxide and oxygen. 

2S^0'=4S0' + 0'^ 



Water dissolves it with production of dense fumes and a 
brisk effervescence due to the disengagement of oxygen. The 
liquid then contains sulphuric acid. At the same time a small 
quantity of persulphuric acid, H^S^O^ or HSO*, is formed, 
which soon decomposes into sulphuric acid and oxygen. 

This persulphuric acid, which is very unstable, would be 
analogous to permanganic acid ; its formation is expressed by 
the following equation : 

S^O^ + ffO == 2HS0* 



SELENIUM AND TELLURIUM. 121 

According to Berthelot, persulphuric acid is formed by the 
electrolysis of concentrated solutions of sulphuric acid. The 
potassium salt is obtained by electrolyzing a saturated solution 
of potassium acid sulphate ; the salt being obtained at the 
anode, which must be artificially cooled. 

2KHS0* + = H^O + 2KS0* 

Barium persulphate, Ba(SO*)^ + 4H^0, is soluble in water. 

SELENIUM AND TELLURIUM. 

These two rare elements present a great analogy to sulphur. 

Selenium was discovered by Berzelius in certain Swedish py- 
rites. It forms an essential part of but a few rare minerals, but 
appears to be widely distributed accompanying iron and copper 
pyrites. Like sulphur, selenium has two allotropic forms, one 
crystalline, the other vitreous and amorphous. The crystalline 
variety begins to melt above 217°, but liquefies only at 250° 
(Regnault) ; after rapid cooling it solidifies into a dark-brown 
mass. Its density is 4.8 when crystallized, and 4.3 when vit- 
reous. When heated in the air to a temperature above its 
melting-point it takes fire and burns with a blue flame, being 
converted into selenious oxide, SeO^ When sulphurous acid 
is added to a solution of selenious oxide the latter is reduced, 
sulphuric acid is formed, and the selenium is precipitated in 
the form of brown -red flakes. Its compound with hydrogen 
is a colorless gas having a fetid and irritating odor. 

The electrical conductivity of selenium is remarkably modi- 
fied by the action of light : when exposed to direct sunlight it 
conducts the current ten times as well as it does in the dark. 

Tellurium is still more rare than selenium ; it occurs com- 
bined with gold and other metals in certain minerals of Tran- 
sylvania and Hungary, and also in the Rocky Mountain gold 
region in the United States. It has the external appearance 
and the lustre of a metal. Its color is silvery-white ; its den- 
sity 6.25. It melts at about 500°, and can be volatilized at a 
white heat in a current of hydrogen. It has a great tendency 
to crystallize. When heated in the air it burns with a green- 
ish-blue flame, forming tellurous oxide, TeO^. Its compound 
with hydrogen is a gas having an odor analogous to that of 
hydrogen sulphide. 

The following table shows the analogy between the principal 
compounds of sulphur, selenium, and tellurium : 
? 11 



122 



ELEMENTS OF MODERN CHEMISTRY. 



H^S 


H^Se 


H^Te 


Hydrogen sulphide. 


Hydrogen selenide. 


Hydrogen telluride. 


SO^ 


SeO^ 


TeO'^ 


Sulphurous oxide. 


Selenious oxide. 


Tellurous oxide. 


SO^ 


[SeO^ 


TeO^ 


Sulphuric oxide. 


Se enic oxide. 


Telluric oxide. 


[H^SOT 


H^SeO=^ 


H^TeO^ 


Sulphurous acid. 


Selenious acid. 


Tellurous acid. 


H^SO* 


H^SeO* 


H^TeO* 


Sulphuric acid. 


Selenic acid. 


Telluric acid. 



CHLORINE. 

Density compared to air 2.44 

Density compared to hydrogen 35.18 

Atomic weight CI =35.18 

Chlorine was discovered by Scheele in 1774, and was first 
recognized as an element by Gay-Lussac and Thenard in 1809, 
and by Sir Humpbry Davy in 1810. It is one of the elements 
of common salt, or sodium chloride. 

Preparation. — One part of manganese dioxide in coarse 
powder and six parts of common hydrochloric acid are intro- 




duced into a flask fitted with a safety-tube and delivery-tube 
(Fig. 37). " - - ------ - 



The reaction begins in the cold, 



chlorine gas is 



CHLORINE. 



123 



disengaged, and may be collected over salt water. As soon as 
the disengagement of gas diminishes, it may be re-established 
by the application of a gentle heat. 

It is more convenient to collect the gas by dry displacement, 
and it may be obtained pure and dry by being washed with 
water, then passed through sulphuric acid, and finally through 
a tower, E, containing calcium chloride, as represented in the 
figure. It is then passed, by means of a tube bent at a right 
angle, into a dry jar. The chlorine being heavier than the 
air, collects at the bottom of the jar and gradually drives out 
the air, and the uniform greenish color of the whole of the gas 
in the jar indicates when the latter is completely filled. 

The reaction which takes place in the preparation of chlorine 
is a double decomposition between the manganese dioxide and 
the hydrochloric acid. Water and manganese chloride are 
formed, and chlorine is set free. 

MnO^ + 4HC1 = 2H^0 + MnCl^ + Cl^ 

Manganese dioxide. Hydrochloric acid. Manganese chloride. 

Large quantities of chlorine are required for the manufacture 
of bleaching-powder (page 329). The gas is generally prepared 
in large stone stills (Fig. 38) by the reaction just described; 
the heating is effected by injecting steam, 
and the manganese chloride solution is 
drawn off and treated with milk of lime, 
which precipitates manganous hydroxide, 
Mn(OH)l After washing this, steam and 
air are blown through it, and it is thus 
oxidized to Mn^O* (Weldon). On treat- 
ment with hydrochloric acid this evolves 
chlorine, and the manganese is thus used 
continuously. 

Mn^O* + 8HC1 = 3MnCP + 4H'^0 + CP 

By another process air and hydrochloric 
acid gas are passed over pumice-stone satu- 
rated with cuprous chloride, Cu^CP. The reaction takes place 
in two phases : first cupric chloride and water are formed, and 
the former is decomposed into cuprous chloride and chlorine 
(Deacon). 

Cu^CP + + 2HC1 = 2CuCP + H^O 
2CuCP = Cu^CP + CP 

Physical Properties. — Chlorine is a greenish-yellow gas 





124 ELEMENTS OF MODERN CHEMISTRY. 

having a strong and suffocating odor. A litre of this gas 
weighs 3.16 gr. It may be liquefied at 0° by a pressure of 
six atmospheres. A small quantity of the liquid may easijy 
be prepared in the following manner : 

Some crystals of chlorine hydrate are introduced into a tube 
of thick glass closed at one end and bent in the middle ; the 

other end is then hermetically 
sealed at the blast-lamp. The 
branch containing the crystals is 
then heated in a water-bath, while 
the other branch is cooled in a 
freezing mixture (Fig. 39). The 
hydrate of chlorine breaks up 
into water and chlorine, and the 
greater part of the latter is disen- 
gaged, and condenses by its own 
pressure into a deep-yellow liquid, 
j^iQ^ 39. which collects in the cooler limb 

of the tube (Faraday). 
Chemical Properties. — One volume of water at 8° dissolves 
3 volumes of chlorine ; at 17°, 2.42 volumes. The saturated 
solution has a yellow color. When it is exposed to a tempera- 
ture of 0°, it deposits crystals containing 27.7 per cent, of 
chlorine, and 72.3 per cent, of water, and constituting a hydrate 
of chlorine corresponding to the formula CP -|- lOH^O (Fara- 
<iay). 

Chlorine possesses powerful affinities. It unites directly 
with the greater number of the other elements, and the com- 
bination frequently takes place with such energy that luminous 
heat is produced. 

Experiments. — If powdered antimony or arsenic be sprinkled 
into a jar containing dry chlorine, each particle of the black 
powder burns with a bright spark as soon as it enters the atmos- 
phere of chlorine, producing thick, white fumes of antimony 
or arsenic chloride as the case may be. 

If a morsel of phosphorus, contained in a deflagrating spoon, 
be plunged into a jar of chlorine, the phosphorus melts and 
inflames spontaneously, and the sides of the jar become covered 
with a yellow, crystalline deposit of phosphorus pentachloride, 
PCP. 

But the affinity of chlorine is most strikingly manifested by 
its action on hydrogen and hydrogen compounds. 



CHLORINE. 125 

When a lighted taper is applied to a mixture of equal vol- 
umes of chlorine and hydrogen, the two gases unite instantly 
and explosively. Such a mixture will also explode violently 
on being exposed to direct sunlight ; the rays of the sun may 
even be replaced by the flame of magnesium or that of carbon 
disulphide. 

So great is the affinity of chlorine for hydrogen that it de- 
composes all hydrogen compounds, except hydrochloric and 
hydrofluoric acids. When it is dissolved in water, it slowly 
decomposes that liquid under the influence of sunlight, com- 
bining with the hydrogen and setting the oxygen at liberty. 

If a tube filled with an aqueous solution of chlorine be 
inverted over the pneumatic trough and exposed to direct sun- 
light, small bubbles of gas will be seen to rise through the liquid 
and collect at the top of the tube. This is the oxygen result- 
ing from the decomposition of the water. 

At a red heat, the vapor of water is rapidly decomposed by 
chlorine ; hydrogen sulphide gives up its hydrogen to chlorine 
at ordinary temperatures. 

All organic substances contain hydrogen ; they are therefore 
generally modified, and often destroyed by the action of chlorine. 
Coloring matters of organic origin are bleached. 

Experiment. — If a solution of chlorine be added to a solu- 
tion of litmus, sulphate of indigo, or ink, the intense colors 
peculiar to these substances disappear, giving place to a pale 
yellow or brown tint. This efl"ect is due to the more or less 
profound decomposition which these coloring matters undergo 
by reason of the removal of a certain portion of their hydro- 
gen in the form of hydrochloric acid. 

This bleaching property of chlorine is of great service in the 
arts. 

A wax taper will burn in chlorine gas with a red, smoky 
flame. The hydrogen of the wax combines with the chlorine, 
while the carbon is set free as smoke. A piece of paper satu- 
rated with oil of turpentine takes fire spontaneously when 
introduced into a jar of chlorine, producing a dense cloud of 
smoke ; the turpentine contains only carbon and hydrogen the 
latter is attacked by the chlorine, the former being set free. 

Chlorine is also an efficacious disinfectant. It decomposes 
hydrogen sulphide. It destroys odorous matters of organic 
origin, the effluvia resulting from putrid fermentation, and 
the miasms which are sometimes diffused in the air. It 

11* 



126 ELEMENTS OP MODERN CHEMISTRY. 

is employed to disinfect privys, etc., and to purify the air in 
certain epidemics. 

The bleaching properties and disinfecting properties of 
chlorine are due to the same cause, — its powerftil affinity for 
hydrogen. 

HYDROCHLORIC ACID. 

Density compared to air 1.27 

Density compared to hydrogen 18.33 

Molecular weight HCl == 36.18 

Hydrochloric acid exists among the gaseous products disen- 
gaged by volcanoes. 




Fig. 41. 



Preparation. — Fragments of fused common salt are intro- 
duced into a flask fitted with a safety-tube and delivery-tube, 
like that for the preparation of chlorine, and concentrated sul- 
phuric acid is added. Hydrochloric acid gas is disengaged, and 



HYDROCHLORIC ACID. 



127 



may be collected over mercury. Sodium acid sulphate remains 
in the retort. 

H^SO* + NaCl = NaHSO* + HCl 

Sodium chloride. Sodium acid sulphate. 

In the arts, the operation is conducted in cast-iron cylinders 
or furnaces (Fig. 41), at a high temperature. Under these 
conditions, one molecule of sulphuric acid acts upon two mole- 
cules of sodium chloride, yielding sodium neutral sulphate, 
and two molecules of hydrochloric acid. 

H^SO* + 2NaCl = Na^SO* + 2HC1 

Sodium sulphate. 

The hydrochloric acid gas evolved is passed into stoneware 
bottles, C, C, C, containing water. It is thus dissolved, 
and the solution obtained constitutes the muriatic acid of com- 
merce. 

A solution of hydrochloric acid may be prepared in the 
laboratory by passing the gas through water contained in a 
series of Wolff bottles surrounded by cold water, the contents 
of the first bottle being rejected (Fig. 42). 




Fig. 42. 



Composition of Hydrochloric Acid. — The composition of 
this gas may be deduced from the following experiments : 



128 



ELEMENTS OF MODERN CHEMISTRY. 




Fig 



1. A bottle, B (Fig. 43), the neck of whicli is adapted by 
grinding with emery to the flask A, is filled with dry chlorine ; 

A, which has exactly the same capacity as 
the bottle, is filled with dry hydrogen ; the 
two vessels are then fitted together, and by 
means of the ground joint are hermetically 
sealed. The apparatus is now abandoned 
for a time to diffuse light, and as the two 
gases slowly mix they comlDine. The union 
is completed by exposing the apparatus to 
direct sunlight. When the tint of the 
chlorine has entirely disappeared, the two 
vessels are separated under the surface of 
mercury, and it is found that no change in 
volume has taken place. The chlorine and 
hydrogen have both disappeared to form 
hydrochloric acid, which occupies precisely 
the same volume as the two primitive gases. Consequently 2 
v^olumes of hydrochloric gas contain 1 volume of chlorine and 
1 volume of hydrogen ; and if the weight of one volume of 
hydrogen (unity) be added to that of one volume of chlorine 
(its density compared to hydrogen as unity), the sum will be 
the weight of two volumes of hydrochloric acid, and will also 
represent the weight of the molecule. 

Weight of 1 volume of hydrogen . 
Weight of 1 volume of chlorine . 
Weight of 2 volumes of hydrochloric acid 36.5 2.5093 

2. Two volumes of hydrochloric acid gas are passed into a 
~ 44), and a small piece of sodium 

is passed up into the bulb and 
heated by the flame of a spirit- 
lamp. The sodium combines 
with the chlorine setting the 
hydrogen at liberty, and after 
the experiment one volume of 
hydrogen remains in the tube. 
This second experiment con- 
firms the first, both proving 
that hydrogen and chlorine 
unite in equal volumes, and 
without condensation, to form 



ensities com- 


Densities com- 


pared to H. 


pared to Air, 


. 1 


0.0693 


. 35.5 


2.44 



bent tube over mercury (Fig 




Fig. 44. 



HYDROCHLORIC ACID. 



129 



hydrocMoric acid. One volume of hydrocliloric acid contains 
half a volume of hydrogen and half a volume of chlorine, but 
we cannot admit that the atoms of these element^ are divided 
into two in the formation of hydrochloric acid ; such a sup- 
position would be contrary to all ideas of atoms, which repre- 
sent the smallest particles of an element that can exist in a 
compound. It is more natural to conclude that two vol- 
umes of chlorine and two volumes of hydrogen react together 
in the formation of hydrochloric acid. Two volumes of 
chlorine contain two atoms, constituting one molecule of chlo- 
rine. In the same manner two volumes of hydrogen contain 
two atoms, constituting one molecule of hydrogen. 



CI 


CI 



H 


H 



2 volumes or 1 molecule of 
chlorine = ClCl. 



2 volumes or 1 molecule of 
hydrogen = HH. 



It is these molecules which are separated into two when 
chlorine combines with hydrogen : they exchange their atoms, 
and from the exchange, which is a double decomposition, there 
result two molecules of hydrochloric acid, which occupy pre- 
cisely the same volume as the two molecules of the simple gases. 



CI 


CI 


+ 


H 


H 


= 


H CI 


+ 


H 


CI 



2 vols, of chlorine + 



of hydrogen 



2 vols, of hydro- + 2 vols, of hydro- 
chloric acid chloric acid. 



We encounter here again the notion that certain elements in 
the free state are composed of molecules, each of which con- 
tains two atoms of the same kind. The force which unites 
them is not different from affinity. It is affinity which. unites 
chlorine to chlorine in the molecule of that element ; hydrogen 
to hydrogen in the molecule of free hydrogen (Grerhardt). 
When, however, these two molecules are brought together, the 
affinity of chlorine for hydrogen preponderates, and brings about 
an exchange, a double decomposition. 

Physical Properties. — Hydrochloric acid is a colorless gas 
having a pungent odor. It forms thick white fumes in the air 
by condensing the atmospheric moisture. It may be liquefied 
by a pressure of 40 atmospheres. 

It is one of the most soluble of gases in water. If a jar 
filled with this gas and inverted on a plate containing mercury 



130 ELEMENTS OF MODERN CHEMISTRY. 

SO that the mouth is sealed, be depressed in the pneumatic 
trough, and the plate be then quickly removed, the water im- 
mediately rushes into the jar as it would into a vacuum. The 
shock of the column of water is sometimes sufficient to break 
the jar. 

One volume of water at 0° dissolves 500 volumes of hydro- 
chloric acid; at ordinary temperatures, about 480 volumes. 
The water becomes heated and increases in volume. The cold 
saturated solution has a density of 1.21 and contains 42.4 
per cent, by weight of the dry gas. It is a colorless liquid, 
giving ofi" white fumes. When it is heated, it loses a large 
quantity of the gas which it holds in solution, but the whole 
of the gas is not disengaged, and when the temperature reaches 
110° the liquid distils without further loss of gas. A dilute 
hydrochloric acid is thus obtained, having a uniform density of 
1.10 and containing 20.24 per cent, of the acid. 

Chemical Properties. — Hydrochloric acid is an energetic 
acid ; it strongly reddens litmus-paper. It is not decomposable 
by heat, but is partly decomposed by a series of electric sparks. 
All of the metals which decompose water also decompose hy- 
drochloric acid with the liberation of hydrogen and the for- 
mation of a chloride. Such metals are sodium, zinc, iron, 
aluminium, tin, etc. 

Hydrochloric acid decomposes the metallic oxides and hy- 
droxides with the formation of water and a chloride. 

If hydrochloric acid be added in small quantities to a con- 
centrated solution of potassium hydroxide, the liquid becomes 
heated and deposits potassium chloride as a crystalline powder. 

HCl -f KOH = KCl H- H^O 

Potassium hydroxide. Potassium chloride. 

Hydrochloric acid is then a true acid, although it contains no 
oxygen, for it contains an atom of hydrogen that is replaceable 
by an atom of metal. In its action upon potassium hydroxide 
it resembles nitric acid, for this acid also contains one atom of 
hydrogen, which is replaceable by an atom of metal. 

HNO^ + KOH = KNO^ + H^O 

Nitric acid. Potassium nitrate. 

It is seen that the acids are compounds containing a strongly 
electro-negative atom or group of atoms, united with hydrogen, 
which hydrogen can be replaced by a metal. In nitric acid, 
H(NO^), the group NO^ plays the part taken by chlorine in 



OXYGEN COMPOUNDS OF CHLORINE. 131 

hydrochloric acid ; like the chlorine, it renders the hydrogen 
replaceable by a metal. 

The action of hydrochloric acid upon the metallic oxides is 
analogous to that which it exerts upon the hydroxides. 

If a current of hydrochloric acid be passed over mercuric 
oxide contained in a tube (Fig. 45), the oxide becomes heated, 




Fig. 45. 

and is converted into a white powder which is mercuric chlo- 
ride ; at the same time water is formed and condenses in the 
bulb. 

HgO + 2HC1 = HgCP + WO 

Mercuric oxide. Mercuric chloride. 

OXYGEN COMPOUNDS OF CHLORINE. 

With oxygen, chlorine forms compounds which may be 
anhydrous or hydrated ; the latter are acids. 
The oxides are : 

Hypoclilorous oxide Cl^O 

Chlorine peroxide ClO^ 

The acids are : 

Hypochlorous acid HCIO 

Chloric acid HCIO» 

Perchloric acid HCIO* 



132 



ELEMENTS OP MODERN CHEMISTRY. 



HYPOCHLOROUS OXIDE. 
CPO 

Hypochlorous oxide is prepared by passing a current of dry 
clilorine over mercuric oxide contained in a tube surrounded 
by cold water, and may be condensed in a long-necked matrass 
placed in a freezing mixture (Fig. 46). 



HgO + 

Mercuric oxide. 



2CP 



= HgCP + 

Mercuric chloride. 



CPO 




Tig. 46. 



The oxide condenses as a brown-red liquid, boiling at 5°. 
Above that temperature it is a reddish-yellow vapor, having a 
density of 2.977, or, compared to hydrogen as unity, 43.5. 
Two volumes of this vapor contain two volumes of chlorine 
and one volume of oxygen, a composition represented by the 
formula CPO. 

Hypochlorous oxide is a dangerous body, and cannot be kept 
for more than a few hours without spontaneous decomposition ; 
its vapor frequently explodes. 

In combining with the elements of water, hypochlorous oxide 
forms hypochlorous acid, the solution of which is almost color- 



}o + i}o = ci}o + ^> 



HYPOCHLOROUS ACID. 133 

HYPOCHLOROUS ACID. 

HCIO 

This acid lias never been obtained in the pure state. An 
aqueous solution may be prepared by agitating mercuric 
oxide with water in jars filled witb chlorine gas. The water 
will tben contain hypochilorous acid and mercuric chloride, 
and tbere remains a brown powder, wMcb is mercury oxy- 
chloride. (Balard.) 

2HgO + ffO + 2CP = HgO.HgCP + 2HC10 

Another method consists in passing chlorine through water 
holding recently-precipitated calcium carbonate in suspension. 
The latter disappears, carbonic acid gas is disengaged, and the 
water becomes charged with calcium chloride and hypochlorous 
acid. The mixture is distilled, and the acid which passes with 
the water is condensed in a cooled receiver (Williamson). 

CaCO^ + 2CP + H^O = CO^ + CaCP + 2HC10 

Calcium Carbon Calcium Hypochlorous 

carbonate. dioxide. chloride. acid. 

When chlorine is passed into a rather dilute solution of an 
alkaline hydrate, a chloride and a hypochlorite are formed : 
2K0H + 2C1 = KCl H- KCIO + H^O 

In this manner are prepared solutions containing potas- 
sium hypochlorite (eau de Javelle), and sodium hypochlorite 
(Labarraque's solution), extensively used for bleaching and 
disinfecting. The most important hypochlorite is the cal- 
cium salt, Ca(ClO)^ which is the principal constituent of 
bleaching-powder. 

Properties of Hypochlorous Acid. — Concentrated hypo- 
chlorous acid, obtained by distilling the aqueous solution, is 
a dark-yellow liquid, having the peculiar smell of chlorinated 
lime or bleaching-powder. It is very caustic and rapidly 
destroys the skin ; its bleaching power is very energetic, 
double that of the chlorine it contains. Hydrochloric acid 
decomposes it into chlorine and water. 

HCIO -f- HCl = CP -f H^O 

Hypochlorous acid is very unstable except in dilute solu- 
tions. It decomposes spontaneously into oxygen and hydro- 
chloric acid. 

2HC10 = 2HC1 + 0' 



134 



ELEMENTS OF MODERN CHEMISTRY. 




Fig. 47. 



CHLORINE PEROXIDE. 

C102 

This compound, which was 
discovered by Sir Humphry 
Davy, is prepared by the ac- 
tion of concentrated sulphuric 
acid upon fused potassium 
chlorate. The salt is finely 
pulverized and added in small 
quantities to sulphuric acid 
cooled to —10°. The pasty 
mass is then introduced into 
a small test-tube fitted with a 
delivery-tube (Fig. 47), and 
is gently heated in a water- 
bath ; the gas disengaged is 
collected in dry jars by down- 
ward displacement. 
3KC10^ + 2H2SO* = KCIO^ + 2KHS0* + H'^O + 2C10' 

Potassium Potassium Potassium acid 

chlorate. perchlorate. sulphate. 

Chlorine peroxide is a yellow gas having a strong irritating 
odor. When strongly cooled, it condenses to a dark-red 
liquid, which boils at 9°, and solidifies at — 79°. Compared 
to hydrogen, the density of the gas is 33.47 ; hence the mo- 
lecular weight is 66.94, corresponding to the formula CIO'''. 

A mixture of this gas with chlorine is disengaged when 
hydrochloric acid is heated with potassium chlorate. This 
mixture is called euchloriney and was formerly believed to be a 
definite compound. 

4KC10' + 12HC1 ^ 4KC1 + eH^O + 3C10^ + 9C1 

Chlorine peroxide is a dangerous body ; it sometimes decom- 
poses spontaneously with violent explosions. 

It is soluble in water, and the solution may be prepared by 
passing into water the mixture of carbonic acid gas and chlorine 
peroxide which is evolved when potassium chlorate is heated 
on a water-bath with an equal quantity of oxalic acid. 

It acts as a powerful oxidizing agent. A jet of hydrogen 
sulphide passed into it takes fire spontaneously and continues 
to burn, and on contact with it sugar and other organic com- 



CHLORIC ACID — PERCHLORIC ACID. 135 

pounds are inflamed. If a drop of sulphuric acid be allowed 
to fall on a mixture of equal parts of sugar and potassium 
chlorate, both in powder, the chlorine peroxide disengaged at 
once ignites the sugar in contact with it, and the potassium 
chlorate yields its oxygen for the rapid combustion of the 
entire ma&s. 

Chlorine peroxide is absorbed by alkaline solutions with the 
formation of a chlorate and a chlorite. 

2K0H -J- CW = KCIO^ -f KCIO- -f- H^O 

Pota&sium hydroxide. Potassium chlorate. Potassium chlorite. 

Potassium chlorite is a salt of chlorous acid which has 
never been isolated. 

CHLOEIC ACID. 

HC103 

This acid is formed by the spontaneous decomposition of 
solutions of hypochlorous acid and chlorine peroxide. 

It may be prepared by treating barium chlorate with dilute 
sulphuric acid. Barium sulphate precipitates, and is removed 
by filtration, and the solution of chloric acid is concentrated by 
evaporation in vacuo. 

If chlorine be passed into a concentrated solution of an 
alkaline hydrate, a chloride and a chlorate are formed. 
6K0H + 6C1 = 5KC1 -f KCIO^ - SH^O 

Chloric acid is a syrupy liquid, ordinarily of a yeUow color ; 
it is not very stable ; at a temperature of -40 "^ it commences to 
decompose, and at a higher temperature it is resolved into per- 
chloric acid, chlorine, oxygen, and water. It has extremely 
energetic oxidizing properties ; when concentrated, it at once 
inflames sulphui\ phosphonis. alcohol, and paper. It oxidizes 
sulphurous and phosphorous acids and hydrogen sulphide. 
With hydrochloric acid it forms water and chlorine. 
HCIO^ — 5HC1 = 3H-0 -f 3CT 

PERCHLOPJC ACID. 

HCIO* 

This is the most rich in oxygen of all the chlorine acids, 

and it is a curious circumstance that it is also the most stable. 
It may be prepared by distilling potassium perchlorate with 
concentrated sulphuric acid. When a mixture of one part 
of the former with four parts of the latter is heated to 110°, 
pure perchloric acid distils over first ; but if the distillation 



136 ELEMENTS OF MODERN CHEMISTRY. 

be continued, the liquid in the receiver is gradually converted 
into the crystalline monohydrate, HCIO* + H^O. The pure 
anhydrous acid may be prepared by carefully redistilling this 
hydrate at a temperature of 110°, part of the acid remaining 
in the retort as the dihydrate, 2HC10* + 2H'0, which boils 
at 203°. 

Perchloric acid is a colorless, volatile liquid having a den- 
sity of 1.782 at 15.5°. When strongly cooled, it solidifies to 
a crystalline mass which melts at 15°. It is extremely hygro- 
scopic : absorbing moisture from the air, it emits dense fumes 
of the hydrate. Its contact with water is attended by a hiss- 
ing noise and a great evolution of heat. Its oxidizing powers 
are so energetic that it explodes on contact with paper, wood, 
or charcoal. 

Pure perchloric acid cannot be preserved or distilled : it 
suffers spontaneous decomposition even in the dark, and ex- 
plodes with much violence when it is heated. 

The salts of perchloric acid are very stable compounds. 
Unlike the chlorates, they are not reduced when heated with 
hydrochloric acid. Potassium perchlorate, KCIO*, is almost 
insoluble in water. 

CHLORIDES OF SULPHUR. 

When a current of dry chlorine is passed over sulphur heated 
in a retort, a liquid condenses in the receiver which fumes in 
the air, has a yellow color, and an irritating, fetid odor. This 
is sulphurous cliloride^ S^CP. In order that this compound 
may be formed, the sulphur must be maintained in excess, and 
the operation must be stopped before it has all disappeared. 
The product is purified by rectification, that part being collected 
which passes at 139°. 

When chlorine is passed for several hours through the 
chloride of sulphur just described, the yellow color of the 
latter changes to deep red. The liquid obtained is mobile, 
fumes in the air, and continually disengages chlorine. It can- 
not be distilled without decomposition. The product which 
passes is at first red, but afterwards assumes a lighter color, and 
when the temperature reaches 139° there remains in the retort 
only sulphurous chloride, S^CP. 

The red liquid has a composition which corresponds to the 
formula SCP, It is called perchloride of sulphur. Carius 



BROMINE. 137 

regards it as a mixture of tlie chloride S^CP with a tetra- 
chloride, SCI*, corresponding to sulphur dioxide. 

SO^ sulphur dioxide. 
SCP sulphur tetrachloride. 

This tetrachloride has been prepared by Michaelis, but 
it can only exist at a low temperature ; it decomposes into 
chlorine and sulphurous chloride, S^CP, as soon as it is removed 
from the freezing mixture where it has been condensed. 

The chlorides of sulphur are employed in vulcanizing 
caoutchouc. 

BROMINE. 

Vapor density compared to air 5.393 

Vapor density compared to hydrogen .... 79.34 
Atomic weight Br = 79.34 

Bromine was discovered by Balard in 1826. 

Preparation. — It is obtained by decomposing potassium 
bromide by manganese dioxide and sulphuric acid. Potassium 
sulphate and manganese sulphate are formed, and the bromine 
is liberated. 

2KBr + MnO' + 2WS0' = K^SO* + MnSO* + 2^0 + Br* 

Potassium Manganese Potassium Manganese 

bromide. dioxide. sulphate. sulphate. 

The operation is conducted in a tubulated retort, heated on 
a sand-bath, and the bromine is condensed in a cooled receiver 
fitted to the retort by the aid of an adapter. 

The potassium bromide may be replaced by magnesium 
bromide, which exists in the mother-liquors obtained in the 
manufacture of potassium chloride from carnallite and also in 
certain brine springs. The liberation of bromine from this SJ^lt 
is effected by the action of chlorine, thus — 

MgBr^ + CP = MgCP + Br^ 

Properties. — Bromine is a dark-red liquid, which solidifies 
at —7.3. Its density at 15° is 2.99. It boils at 63°, and at 
ordinary temperatures gives off red, irritating vapors, for its 
vapor tension is considerable even in the cold. It stains the 
skin yellow, and immediately corrodes the tissues. It dissolves 
in about 33 times its weight of water at 15°, forming an orange- 
red solution. At a low temperature it combines with water, 
forming a crystalline hydrate, Br^-j- lOH^O, analogous to that 
formed by chlorine. 

•^ 12* 



138 ELEMENTS OF MODERN CHEMISTRY. 

Bromine dissolves in carbon disulphide, in cUoroform, and in 
ether. 

Experiment. — A small quantity of solution of potassium 
bromide is introduced into a long tube, closed at one end, and 
the tube is then nearly filled with chlorine-water ; when the two 
solutions are mixed, the liquor assumes an orange-red color 
from the liberation of the bromine. The tube is now filled up 
with ether and agitated briskly, the open end being closed with 
the finger. The ether passes through the aqueous solution 
and dissolves out all of the bromine, assuming at the same time 
a dark-red color. 

The affinity of bromine for hydrogen is powerful, but not as 
energetic as that of chlorine. Like chlorine, it has remarkable 
bleaching properties. 

HYDKOBROMIC ACID. 

Density compared to air 2.73 

Density compared to hydrogen 40.5 

Molecular weight HBr = 80.34 

Preparation. — This gas is prepared by the action of water 
upon phosphorus tribromide. 

PBr' + gajO' = lajO' + 3HBr 

Phosphorus tribromide. 3 molecules water. Phosphorous acid. 

The operation may be conveniently conducted in a doubly- 
curved tube (Fig. 48). Into the long branch CD fragments of 
phosphorus are introduced, carefully separated from each other 
by moistened broken glass. The bromine is introduced into 
the bend A. The shorter end is then corked, a. delivery-tube 
adapted to the end D, and the bromine is gently heated until it 
boils. The vapor comes into contact with the phosphorus and 
forms phosphorus tribromide, but this is at once decomposed 
by the water into phosphorous acid and hydrobromic acid. 
The latter may be collected in jars over the mercury-trough. 

Amorphous phosphorus may be advantageously employed in 
this operation, and the process conducted as directed for hydri- 
odic acid (Personne). 

Another convenient process for preparing the acid depends 
upon the action of bromine on benzene in the presence of 
iron bromide. The gas which is disengaged is purified by 
passing it over ferrous bromide and anthracene. 

When a mixture of hydrogen and bromine vapor is passed 
over heated platinum, the elements unite directly. 



OXYGEN ACIDS OP BROMINE. 



139 



Properties. — Hydrobromic acid is a colorless gas, producing 
dense white fumes in the air. A litre of this gas weighs 3.547 
grammes. It liquefies at — 73°, and may be solidified at a 
lower temperature. It is formed by the union of equal volumes 
of bromine vapor and hydrogen without condensation, so that 
its composition corresponds to that of hydrochloric acid. It 
is very soluble in water ; its concentrated solution fumes in the 
air, and is very corrosive. 

Chlorine decomposes hydrobromic acid, liberating bromine. 




Fig. 48. 



OXYGEN ACIDS OF BROMINE. 

There are known three bromine oxygen acids : 

Hypobromous acid, HBrO 
Bromic acid, HBrO^ 
Perbromic acid, HBrO* 

They correspond to hypochlorous, chloric, and perchloric acids. 

Hypobromous Acid, HBrO. — When mercuric oxide is 
agitated with an aqueous solution of bromine, a yellowish 
liquid is obtained which contains hypobromous acid, and can 
be distilled in vacuo. W. Dancer has obtained this acid by the 
action of bromine upon silver oxide suspended in water. 

2Br^ _|_ Ag^O + H^O = 2AgBr -f- 2HBrO 

Silver oxide. Silver bromide. 

In this process it is necessary to operate rapidly and avoid 



140 ELEMENTS OF MODERN CHEMISTRY. 

the contact of an excess of silver oxide with the hypobromous 
acid, as the latter would be destroyed by the oxide with evolu- 
tion of oxygen. 

2HBrO + Ag^O = 2AgBr + H^O + 0^ 

The solution of hypobromous acid has a yellow color and 
bleaching properties analogous to those of hypochlorous acid. 

Bromie Acid, HBrOl — Potassium bromide and potassium 
bromate are formed by the action of bromine upon a concen- 
trated solution of potassium hydroxide. This reaction is simi- 
lar to that of chlorine upon potash. 

Kammerer recommends the preparation of bromie acid by 
the action of chlorine upon bromine in presence of water. 

5CP + Br^ -f 6W0 = lOHCl -f 2HBrO' 

The hydrochloric acid is driven out by evaporation, and 
bromie acid remains in the form of a liquid that cannot be con- 
centrated to a syrupy consistence without partial decomposition. 

Perbromic Acid, HBrO*. — Kammerer has obtained this 
acid by decomposing perchloric acid with bromine : chlorine is 
disengaged. After concentration on a water-bath, the per- 
bromic acid remains as a colorless oily liquid. It is relatively 
stable, as are the corresponding chlorine and iodine acids. Like 
them, it resists the reducing action of sulphurous acid and 
hydrogen sulphide. 



IODINE. 



Vapor density compared to air 8.716 

Vapor density compared to hydrogen 125.9 

Atomic weight I = 125.9 

Iodine was discovered by Courtois in 1811, and was studied 
by G-ay-Lussac in 1813 and 1814. 

Natural State. — Iodine is widely disseminated in nature. 
It is found in the mineral kingdom combined with various 
metals, such as potassium, sodium, calcium, magnesium, silver, 
mercury. The alkaline iodides exist in small quantity in sea- 
water, in a great number of salt-springs, and in certain rock- 
salts. The sodium nitrate found native in Chili contains traces 
of sodium iodate, and the mother-liquors from which the nitrate 
has been deposited contain enough iodate to be profitably 
employed for the preparation of iodine. The ashes of certain 



IODINE. 141 

sea-plants, such as the algae and fuci, are among the chief 
sources of iodine. 

Preparation. — The ashes of sea-weeds, called kelp, are ex- 
hausted with water and the solution concentrated. Various 
salts, such as sodium and potassium sulphates and chlorides 
and sodium carbonate, are deposited, and the potassium iodide, 
which is contained in smaller quantity than these salts, remains 
in the mother-liquor. 

A regulated current of chlorine is passed into this solution 
as long as it continues to set free iodine, which is deposited as 
a pulverulent, black precipitate. An excess of chlorine must 
be avoided, as this would redissolve a portion of the iodine, 
forming iodine chloride. 

Still larger quantities of iodine are obtained from Chili salt- 
petre : the mother-liquor from the nitrates, which contains all 
the iodine in the form of iodates, is treated with the exact 
quantity of sulphur dioxide required for its decomposition. 

2NaI0^ 4- 5S0^ + 4H^0 ^ P + 4.WS0' + Na^SO* 

Impure iodine is precipitated and is refined by sublimation. 
In the laboratory, iodine is set free from the iodides by the 
action of nitric acid, a nitrate being formed and red vapors 
disengaged. 

Properties of Iodine. — The iodine obtained by sublimation 
occurs as scales or crystalline plates, having a brilliant, dark 
bluish-gray surface, and a density of 4.948 at 17°. It may be 
obtained crystallized in rhombic octahedra by exposing to the 
air a solution of hydriodic acid. 

Iodine melts at 107°. It boils at about 175°, but volatiHzes 
sensibly at ordinary temperatures. Its vapor has an intense 
violet color. A litre of this vapor weighs 11.32 grammes. 

Above 700° the density of iodine vapor diminishes, while 
its color becomes deep blue. At very high temperatures the 
molecule appears to be dissociated into single atoms. 

Iodine is but very slightly soluble in water ; one part of 
iodine requires 7000 parts of water for its solution, but com- 
municates a light-brown color to the whole of that liquid. 
Alcohol and ether dissolve iodine freely, forming dark-brown 
solutions. Carbon disnlphide, benzine, and chloroform also 
dissolve it, assuming a beautiful violet color. 

Experiment. — If a few drops of chlorine-water be added to 
a very dilute solution of potassium iodide, the chlorine will 



142 ELEMENTS OF MODERN CHEMISTRY. 

combine with the potassium, displacing the iodine, which will 
color the liquid brown ; if now the solution be agitated with a 
small quantity of chloroform, the latter will take up all of the 
iodine, assuming a violet color. 

Iodine strikes an intense blue color with starch. The reac- 
tion is very delicate and permits the detection of the smallest 
trace of free iodine. 

Experiment. — If a few drops of a solution of potassium 
iodide be added to a solution of starch, no coloration takes 
place, because the iodine is in combination ; but if a drop or 
two of chlorine-water be added, the iodine will be set free, and 
combining with the starch will at once produce the character- 
istic blue color. An excess of chlorine will again destroy the 
color. 

HYDRIODIC ACID. 

Density compared to air 4.443 

Density compared to hydrogen 64.1 

Molecular weight HI =126.9 

Preparation. — Hydriodic acid is prepared by the action of 
iodine upon phosphorus in presence of water ; phosphorus 
triiodide is first formed, and this is decomposed into phos- 
phorous acid and hydriodic acid. 



PP + |aj0' = lajO' + 

Phosphorus 3 molecules Phosphorous 

triiodide. of water. acid. 



SHI 



Amorphous phosphorus in powder is introduced into a glass- 
stoppered retort the neck of which is soldered to the delivery- 
tube (Fig. 49), and covered with a layer of water ; the iodine 
is then added, and on the application of a gentle heat a regular 
current of hydriodic acid is obtained. The gas may be col- 
lected, like chlorine, by downward displacement in dry jars. 

Properties. — Hydriodic acid is a colorless gas producing 
white fumes in the air. It may be condensed to a colorless 
liquid by strong pressure or intense cold, and can even be solid- 
ified. Dry oxygen decomposes it at a high temperature, water 
being formed and the iodine being set at liberty. 

If a lighted taper be applied to a mixture of hydriodic acid 
and oxygen, the violet vapor of the iodine set free is instantly 
apparent. 

This decomposition of hydriodic acid by oxygen takes place 
at ordinary temperatures in the presence of water. A solution 



HYDRIODIC ACID. 143 

of hydriodic acid exposed to tlie air rapidly becomes brown, 
and after a time deposits crystals of iodine. 

Solution of bydriodic acid is prepared by passing the gas into 
water cooled to 0°. It may also be made by passing a current 
of hydrogen sulphide through water holding iodine in suspen- 
sion ; hydriodic acid is formed, and sulphur is precipitated, 
H^S + P = 2HI + S 

The solution of hydriodic acid saturated at 0° has a density 
of 2, and fumes in the air. When freshly prepared, it is color- 




FiG. 49. 

less ; when heated, it loses part of its gas, and finally distils 
without further alteration at 126°. The solution then con- 
tains 57.7 per cent, of hydriodic acid. 

Chlorine and bromine at once decompose hydriodic acid, 
combining with the hydrogen and setting free the iodine. The 
experiment may be made by pouring a few drops of bromine 
into a jar filled with hydriodic acid gas, when the appearance 
of a violet vapor immediately indicates the liberation of iodine. 

Potassium, zinc, iron, mercury, and silver decompose hydri- 
odic acid, but with unequal energies, setting free the hydrogen. 



144 ELEMENTS OP MODERN CHEMISTRY. 

Sulphuric acid also decomposes it, and is itself reduced to suL 
phurous oxide. 

ffSO* + 2HI = 2W0 + so^ + r 

Nitric acid is still more readily reduced by hydriodic acid. 
2HN0^ + 2HI = 2ffO -f 2N0^ + P 

Nitric acid. Nitrogen peroxide. 

OXIDE AND OXYGEN ACIDS OF IODINE. 

The only oxide of iodine known with certainty is the pen- 
toxide, PO^ It combines with water to form iodic acid, 
HIO^ or HTO^ There is also a periodic acid, H^IO^ corre- 
sponding to the unknown heptoxide, PO^ 

IODIC ACID. 

H2I206 

Iodic acid is formed when iodine is subjected to the action 
of energetic oxidizing agents, such as concentrated nitric acid 
or a mixture of nitric acid and potassium chlorate. It is also 
formed by the action of an excess of chlorine on iodine in 
presence of water. 

p _|- 5CP -I- 6H^0 == lOHCl + H^PO« 

Preparation. — Iodic acid may be conveniently prepared by 
heating iodine and potassium chlorate with dilute nitric acid. 
The oxygen of the chlorate oxidizes the iodine to iodic acid, 
and on adding barium nitrate to the liquid, barium iodate is 
precipitated. The latter salt is decomposed by sulphuric acid ; 
iodic acid is set free in the solution, and barium sulphate is 
precipitated ; the filtered solution is concentrated by evapora- 
tion in vacuo. 

Properties. — Iodic acid is solid, and crystallizes in hex- 
agonal tables. When heated to 170° it loses water and is 
converted into iodic oxide, and at a red heat the latter is 
decomposed into iodine and oxygen. 

It is seen that iodic acid is much more stable than its ana- 
logue, chloric acid ; nevertheless it is easily reduced by bodies 
avid of oxygen. 

If sulphurous acid be added to a solution of iodic acid, a 
precipitate of iodine is formed instantly, but an excess of sul- 
phurous acid redissolves the precipitate, part of the water being 
decomposed and hydriodic and sulphuric acids being formed. 



PERIODIC ACID. 145 

Iodic acid is also decomposed by hydriodic acid. If a solu- 
tion of iodic acid be poured into a solution of starch, no color- 
ation appears, but the characteristic blue color is at once 
developed on adding a drop of hydriodic acid. 

HTO« -f lOHI = GH^O -f 6P 

PERIODIC ACID. 
H5I06 = IO(OH)5 
This acid has been obtained from disodic periodate, a salt 
which is precipitated when chlorine is passed through a solu- 
tion of sodium iodate mixed with sodium hydroxide. 
Na^PO^ -f 6NaOH + 2CP = 2Na2H^IO« + 4NaCl 

Sodium iodate. Sodium hydroxide. Disodic periodate. Sodium chloride. 

The precipitate is dissolved in nitric acid, and lead nitrate is 
added to the solution ; lead periodate is precipitated, and this 
salt is exactly decomposed by sulphuric acid ; the liquid is fil- 
tered to separate the lead sulphate, and evaporated at a gentle 
heat. Periodic acid crystallizes out in colorless, deliquescent, 
rhombic prisms. It melts at 133°. When heated to 140°, 
it is decomposed into iodine pentoxide, water, and oxygen. 
2W10' = PO^ -f 5H^0 + 0' 

Between 180 and 190° periodic oxide abandons oxygen, and 
is converted into iodic oxide, PO^. 

Analogy between Chlorine, Bromine, and Iodine. — 

Chlorine, bromine, and iodine present a striking analogy in their 
chemical properties, and this analogy is seen in all of their com- 
pounds. They combine with hydrogen, atom for atom, forming the 
acids HCl, HBr, HI, and the atoms of chlorine, bromine, and iodine 
are equivalent to each othei- and to an atom of hydrogen ; each of 
these elements is monatomic. 

Their affinities for hydrogen are far from being equal ; in this respect 
chlorine is more powerful than bromine, and bromine than iodine. 
The contrary has been noticed regarding their affinities for oxygen, for 
the oxygen acids of iodine are more stable than those of chlorine. 

The analogy between these three elements is followed out in the 
constitution of their oxides and acids, and in their combinations with 
the metals. The chlorides, iodides, and bromides possess in general 
the same constitution, and it is to be remarked that the greater num- 
ber of these binary compounds are soluble in water and are crystal- 
lizable like salts, of which they otherwise present the characters. 
Hence the name halogen bodies, which was applied by Berzelius to 
this group of elements, to indicate that they form salts in combining 
with the metals. 

G ^ 13 



146 



ELEMENTS OF MODERN CHEMISTRt. 



FLUORINE. 

F = 19 

Fluorine "belongs to ttie group of elements just considered, but its 
chemical energy is much greater than that of chlorine. It occurs 
chiefly in combination with calcium, and also with aluminium and 

sodium, forming the 
minerals fiuor spar, 
CaF^, and cryolite, 
AlF3.3NaP. It was 
first isolated by Mois- 
san, who obtained it by 
the electrolysis of an- 
hydrous hydrofluoric 
acid in which hydrogen 
potassium fluoride was 
dissolved in order to 
give the necessary elec- 
trical conductivity. The 
decomposition was ef- 
fected in a U-shaped 
tube of platinum (Fig. 
50) , each limb of which 
was provided with a 
side tube, and closed 
with a fluor spar stop- 
per carrying and insu- 
lating the platinum 
electrodes. To prevent 
the escape of hydro- 
fluoric acid, this appa- 
ratus was cooled to 
— 40° by the rapid 
evaporation of methyl chloride surrounding it. A battery of 20 
Bunsen cells furnished the current. 

The affinities of fluorine are so energetic that it cannot be collected 
like other gases. It acts violently upon water, and readily combines 
with mercury, but may be received by dry displacement in platinum 
vessels. Fluorine has a greenish-yellow color and a powerful odor. 
Its density is 1.26. At — 187° the gas condenses to a yellow liquid. 
Fluorine combines with hydrogen even in the dark, and with 
explosive violence. Arsenic, antimony, sulphur, phosphorus, and 
silicon ignite spontaneously in the gas, and all the metals combine 
with it directly and, with few exceptions, at ordinary temperatures. 
Chlorine is displaced by fluorine in most of its compounds. Hydro- 
fluoric acid and ozone result from its action upon water. Organic 
compounds, such as alcohol, benzene, turpentine, and even cork, are 
violently attacked and inflamed by it. 

Fluorine does not combine with oxygen or argon. 




HYDROFLUORIC ACID. 



147 



HYDROFLUORIC ACID. 



Molecular weiarht HF 



20 



This compound is prepared by decomposing powdered cal- 
cium fluoride with sulphuric acid. 

CaF=^ + H^SO* = CaSO^ + 2HF 

Calcium fluoride. Calcium sulphate. 

The operation is conducted in a leaden retort, to which is 
adapted a receiver of the same metal surrounded by a freezing 
mixture (Fig. 51). 
The hydrofluoric 
acid condenses as 
a very acid liquid, 
which fumes strong- 
ly in the air. Its 
density is 1.06. In 
this state it still re- 
tains water ; but 
Fremy obtained it ^ 
anhydrous by de- ^j 
composing dry hy- ^^^^^^^p^ 
drogen potassium 

double fluoride KF, Fig. 51. 

HF, by heat in a 

platinum retort. This salt breaks up into potassium fluoride, 
which remains, and hydrofluoric acid, which is disengaged and 
must be condensed in a platinum receiver cooled to — 20°. 
Pure hydrofluoric acid is liquid at ordinary temperatures ; it 
is very mobile, it freezes at — 92.3° and boils at 19.4°. It is 
extremely corrosive, and manipulations with it should be con- 
ducted with great care. Its afiinity for water is so great that 
each drop of the acid let fall into that liquid produces a hissing 
noise, as would a red-hot iron. The solution is employed for 
etching upon glass, for hydrofluoric acid attacks and corrodes 
that substance. This efl'ect is due to the action of the acid 
upon the silica of the glass, which it converts into either sili- 
con fluoride or hydrofluosilicic acid, as will be seen farther on. 

A design may readily be engraved on glass by covering the 
glass with a thin coating of wax, through which the design is 
traced with a sharp point ; the glass is then placed over a leaden 
capsule containing a mixture of powdered calcium fluoride and 




148 



ELEMENTS OF MODERN CHEMISTRY. 



strong sulphuric acid, which is gently heated by a spirit-lamp. 
Hydrofluoric acid vapor is disengaged and attacks the glass 
wherever it is not protected by the wax. When the wax is re- 
moved, the design is found to be permanently etched on the glass. 
A dilute solution of hydrofluoric acid or a bath of hydro- 
fluoride of potassium fluoride may be employed instead of tbe 
vapor in the former experiment, but in this case the etched 
portions are transparent and not opaque as when produced by 
the vapor ; they may be rendered opaque by adding a salt, such 
as potassium or ammonium sulphate, to the bath. 



NITROGEN. 

Density compared to air 0.969 

Density compared to hydrogen 13.93 

Atomic weight N = 13.93 

Nitrogen was discovered by Eutherford in 17V2. It is one 
of the elements of the air, and was first obtained free from 
oxygen by Lavoisier and Scheele, in 1777. 

Preparation. — A flat piece of cork, B (Fig. 52), floating in 
the pneumatic-trough, supports a small capsule containing a 
fragment of phosphorus. The latter 
is inflamed, and the capsule immedi- 
ately covered with a bell-jar. The 
heat produced by the combustion at 
first expands the air and drives out 
a portion, but in a few minutes the 
water rises in the jar, taking the 
place of the oxygen which has been 
consumed. When the phosphorus is 
extinguished, the experiment has ter- 
minated. The water gradually dis- 
solves the white smoke of phosphoric 
oxide which fills the jar, and there 
remains a colorless, irrespirable gas 
that will not support combustion. This gas is nitrogen, still 
mixed with argon, traces of oxygen, and carbonic acid gas. 

Nitrogen containing no impurity except argon may be ob- 
tained by passing a current of air, previously freed from moisture 
and carbon dioxide, through a porcelain tube containing incan- 
descent copper. The copper absorbs the oxygen, and nitrogen 




Fig. 52. 



AMMONIA. 149 

passes out at the end of the tube and may be collected over 
the pneumatic trough. 

Pure nitrogen is best obtained by heating a strong solution 
of ammonium nitrite ] the products are nitrogen and water. 

(NH4)N0' = 2H^0 -f N^ 

Ammonium nitrite. 

Properties. — Nitrogen is a colorless gas, somewhat lighter 
than the air. A litre of this gas weighs 1.2505 grammes. It 
extinguishes burning bodies, and is not combustible itself ; it 
produces no precipitate in lime-water. Water dissolves only 
-^ of its volume of nitrogen at 0°. Animals are quickly suffo- 
cated in an atmosphere of pure nitrogen, but the gas does not 
exert a poisonous influence upon the economy. 

It can be liquefied at temperatures below — 146° (its critical 
temperature). Its critical pressure is 35 atmospheres. Under 
a pressure of one atmosphere this liquid boils at — 190°. The 
affinities of nitrogen are not energetic. It combines directly 
with only a very small number of elements, among which may be 
mentioned magnesium, silicon, boron, and titanium. Under the 
influence of electrical discharges it will unite with oxygen, form- 
ing nitrogen peroxide, and with hydrogen, forming ammonia. 

There are at present known three compounds of nitrogen 
and hydrogen, — ammonia, NH^, hydrazine, N^H*, and hydra- 
zoic acid, N^H. 

AMMONIA. 

Density compared to air 0.596 

Density compared to hydrogen 8.60 

Molecular weight NH^ = 16.93 

Ammonia was discovered by Priestley, studied by Scheele, 
and analyzed by Berthollet in 1785. 

Preparation. — Equal weights of quick-lime and sal am- 
moniac, both in powder, are rapidly mixed in a mortar, and 
the mixture introduced into a glass flask, which is then filled 
up with fragments of quick-lime. A cork and delivery-tube 
are adapted to the flask, which is then gently heated and the 
gas disengaged collected over mercury. 

The calcium oxide or lime decomposes the ammonium 
chloride (sal ammoniac), with the formation of calcium 
chloride, ammonia gas, and water; the latter is absorbed by 
the fragments of lime which fill up the flask. 

2NH^C1 -f CaO = 2NH^ + CaCP + H^O 

Ammonium chloride. Calcium oxide. Ammonia. Calcium chloride. 

13* 



150 



ELEMENTS OF MODERN CHEMISTRY. 



A solution of ammonia in water may be prepared by passing 
the gas tbrougb a series of Wolff's bottles, about balf filled with 
water, excepting the first, which should only contain a small 
quantity destined to wash the gas. 

Physical Properties. — Ammonia is a colorless gas, having 
a powerful and pungent odor, which excites tears. Its taste is 
burning and caustic. It may be. liquefied by a temperature of 
— 40°, or at 10° under a pressure of 6i atmospheres. Fara- 
day's method of liquefying it is as follows : ammonia is passed 
over dry silver chloride, by which it is absorbed. The silver 
chloride, saturated with ammonia, is introduced into a bent 
tube (Fig. 53), the empty limb of which is then sealed at the 





Fig. 63. 



Fig. 54. 



blow-pipe. The end containing the chloride is now heated in 
a water-bath, while the empty end is cooled in a freezing mix- 
ture (Fig. 54). The ammonia is driven out from the silver 
chloride, and condenses into a transparent liquid in the cooler 
branch. Faraday succeeded in solidifying ammonia by subject- 
ing this liquid to rapid evaporation. In the solid state it is a 
white, crystalline, transparent substance, fusible at — 75°, and 
having only a feeble odor. According to Bunsen, liquid am- 
monia boils at — 33.7° ; its density at 0° is 0.6233. 

Ammonia gas is very soluble in water, which dissolves 1000 
times its volume at 0°, and about 740 times its volume at 
15°. The rapid absorption of ammonia by water may be strik- 
ingly shown by the following experiment. A bottle, A (Fig. 55) , 
is filled with ammonia gas, and fitted with a cork, through 
which passes a tube drawn out at both extremities, and the 
outer end of which is sealed. If this end be plunged under 
water and the point be broken off, the water at once rises into 



AMMONIA. 



151 



the bottle, forming a fountain, and the vessel becomes filled 

with water in a very short time. 

The aqueous solution of ammonia possesses the odor of the 

gas; it is caustic, and 

was formerly called vol- 
atile alkali and spirits 

of hartshorn. It is 

largely used in the arts 

and as a reagent. Its 

density is 0.882 at 15°. 

When heated, it loses 

ammonia gas, the whole 

of which may be driven 

out by boiling. 

Composition of Am- 
monia. — 200 volumes 
of ammonia gas are in- 
troduced into an eudi- 
ometer, and electric 
sparks are passed 
through the gas for 
some time by means of 
a RuhmkorfF coil (Fig. 
56). ^ When the experiment has terminated, the volume of 
gas will be found to have doubled. 200 volumes of oxygen 
are added to the 400 volumes of gas thus obtained, and a spark 
is passed; an explosion takes place, and after making the 





Fig. 56. 
necessary corrections for temperature and pressure, the 600 
volumes of gas are found to be reduced to 150 volumes ; 450 
volumes have thus disappeared to form water, 



152 



ELEMENTS OF MODERN CHEMISTRY. 



These 450 volumes must have contained 

300 volumes of hydrogen, 
150 volumes of oxygen. 

Consequently the 200 volumes of ammonia gas, which were 

decomposed by the spark into 400 volumes, must have been 

formed by the union of 

300 volumes of hydrogen, 
100 volumes of nitrogen. 

The latter gas remains in the eudiometer, together with the 
50 volumes of oxygen that were employed in excess. 

From this analysis it is seen that two volumes of ammonia 
contain three volumes of hydrogen and one volume of nitrogen, 
a composition which is expressed by the formula NH^. 

Chemical Properties. — Ammonia gas is decomposed by a 
high temperature, as by a series of electric sparks. The experi- 
ment may be made by passing the gas through a porcelain tube 




filled with fragments of broken porcelain and heated to white- 
ness, and collecting the gas resulting from the decomposition in 
vessels filled with water (Fig. 57). This gas is found to be a 
mixture of three volumes of hydrogen and one volume of 
nitrogen. 

The decomposition takes place more readily if iron, copper, 
or platinum wires be introduced into the porcelain tube. The 



AMMONIA. 



153 




Tig. 58. 



latter metal is not altered, but the iron and copper become 
brittle and retain a few per cent, of nitrogen. The decompo- 
sition of the ammonia seems here to 
be favored by the formation of metallic 
nitrides, unstable compounds which are 
almost entirely decomposed by the pro- 
longed action of the heat. 

Ammonia will not burn in air, but 
will burn in an atmosphere of oxygen. 
A glass tube about 25 millimetres in 
diameter and 15 centimetres long is 
fitted with a cork through which pass 
two bent tubes, one reaching nearly to 
the open end of the tube, the other 
only a little beyond the cork (Fig. 58), 
and some cotton-wool or loose asbestos 
is thrust into the wide tube beyond 
this point. Ammonia gas, conven- 
iently obtained by heating strong am- 
monia water, is passed through the longer tube, while oxygen 
gas is delivered through the shorter. The ammonia may then 
be ignited, and will burn with a yellow 
flame. 4NH» + 30^ = 6H^0 + 2^\ 
A mixture of four volumes of ammonia 
with three of oxygen will explode on the 
application of flame. 

Independently of this rapid combustion, 
ammonia may undergo slow combustion. 
A spiral of platinum wire is suspended 
above a little ammonia water in a beaker 
(A, Fig. 59). The latter is gently heated, 
and oxygen is passed through the liquid. 
The mixed ammonia and oxygen gases 
in contact with the platinum spiral com- 
bine and develop so much heat that the 
spiral is heated to redness. The vessel 
sometimes becomes filled with white fumes 
of ammonium nitrite, produced by the 
slow oxidation of the ammonia. If a 
mixture of oxygen and ammonia be 
passed through a heated tube containing spongy platinum, 
nitric acid and water will be formed and disengaged in vapor. 




Fig. 59. 



154 ELEMENTS OF MODERN CHEMISTRY. 

Action of Chlorine and Iodine upon Ammonia. — Chlorine 

instantly decomposes ammonia, combining with its hydrogen. 
If a drawn-out tube through which a jet of ammonia is escaping 
be plunged into a bottle filled with dry chlorine (Fig. 60), the 
ammonia takes fire immediately, and white vapors of ammo- 
nium chloride are formed. 

4NH3 + CP = 3NH*C1 + N 
If a long tube closed at one end be almost filled with satu- 
rated chlorine-water, and then filled up with ammonia-water, 
and quickly inverted on the pneumatic 
trough, the lighter solution of ammonia will 
rise through the chlorine-water, and reaction 
occurs according to the preceding equation. 
Ammonium chloride remains in solution, 
while the nitrogen collects in the tube. 

Nitrogen Chloride. — Under certain con- 
ditions the nitrogen combines with chlorine, 
forming a very explosive and dangerous 
compound, nitrogen chloride, NOP. This 
is an oily yellow liquid, heavier than water, 
^^^^_^^ which explodes violently on contact with 
'-p ^'TT phosphorus, turpentine, and other combusti- 

ble substances. 

A small jar of chlorine is inverted in a saucer containing a 
solution of ammonium chloride ; the salt is slowly decomposed 
by the chlorine, with the formation of hydrochloric acid and 
nitrogen chloride, and a drop of yellow liquid soon collects on 
the surface. A light tap on the vessel causes it to sink through 
the solution into the saucer. The jar is now removed and a 
small piece of phosphorus pushed into the drop of nitrogen 
chloride by the aid of a long wooden rod. Instantly the nitro- 
gen chloride explodes and the saucer is broken into pieces. 

When a warm saturated solution of ammonium chloride is 
electrolyzed, the chlorine set free at the anode reacts with the 
solution ; nitrogen chloride is formed, and carried to the sur- 
face with the escaping gases. If a little turpentine be poured 
on the surface of the liquid, on contact with this each little 
globule of the chloride explodes with a flash and a continual 
crackling is kept up. 

Nitrogen chloride has been carefully investigated by Gatter- 
mann, who found that it explodes also when exposed to direct 
sunlight. 




AMMONIA. 155 

Nitrogen Iodide. — There is another explosive compound 
analogous to nitrogen chloride, but containing iodine. It is 
obtained as a black powder by treating powdered iodine with 
ammonia ; when dry it explodes with great violence on the 
lightest touch, and sometimes spontaneously. Bunsen has 
attributed to it the formula N^H^Il 

According to Stahlschmidt, the composition of nitrogen iodide 
corresponds to the formula NP, when this body is prepared by 
the action of an alcoholic solution of iodine upon aqueous am- 
monia ; but if both bodies be in alcoholic solution, an iodide 
is obtained having the formula NHI^ If this be correct, 
these bodies present very simple relations with ammonia. 
fH fCl n fl 

1h Ici U (H 

Ammonia. Kitrogen chloride. Triiodammonia. Diiodammonia. 
Trichlorammonia. Nitrogen iodides. 

The last-named compound has been recently carefully studied 
by Szuhay, who obtained it by the action of aqueous solution 
of ammonia upon a strong solution of iodine in potassium 
iodide. Its hydrogen is replaceable by metals. 

Action of Potassium upon Ammonia. — When potassium 
is heated in an atmosphere of ammonia, the brilliant surface 
of the metal becomes covered with a greenish-black liquid, 
and at the same time hydrogen is disengaged. The metal 
entirely disappears little by little, and, on cooling, the liquid 
solidifies to an olive-green mass. This substance represents 
ammonia in which one atom of hydrogen has been replaced 
by an atom of potassium. 

H > N = Ammonia. H > N = Potassium amide. 

It reacts with water, forming ammonia and potassium hydrate. 
KNff -f WO = KOH -I- NH^ 

Potassium amide. Potassium hydrate. 

Ammonium Amalgam. — If liquid amalgam of potassium 
or sodium and mercury be treated with a saturated solution of 
ammonium chloride, the amalgam increases in volume, assumes 
a buttery consistence, and is converted into a soft, light mass 
naving the metallic lustre of mercury. It will retain the im- 
pression of the finger, and will float upon water ; but it grad- 
ually decomposes, losing hydrogen and ammonia, and only 
mercury remains. This unstable body is called ammonium 
amalgam. Whether it is really an amalgam of the group NH* 



156 ELEMENTS OF MODERN CHEMISTRY. 

with mercury or is simply metallic mercury containing hydrogen 
and ammonia gases is still doubtful. 

Although the ammonium group has not been isolated, there 
can be no doubt that it exists in many compounds, and plays 
in them a part analogous to that of a metallic atom. Thus 
ammonium may replace potassium in the potassium salts, pro- 
ducing compounds similar and analogous to the latter. 

NHIHCI = (NH^)Cl analogous to KCl 

Ammonium chloride. Potassium chloride. 

NH^HNO^ == (NH*)NO^ analogous to KNO^ 

Ammonium nitrate. Potassium nitrate. 

NHlffS = ^h}^ analogous to ||s 

Ammonium sulphydrate. Potassium sulphydrate. 

CNH7.ffS = NH*}^ analogous to | 

Ammonium sulphide. Potassium sulphide. 

AMMONIUM CHLORIDE. 

This salt was formerly obtained from Egypt, where it was 
made by subliming the soot produced by the combustion of 
camel's dung. It is now prepared in large quantities from gas- 
liquor, or the water condensed in the manufacture and purifi- 
cation of illuminating gas from coal. This liquor is heated 
with lime, ammonia is disengaged and is conducted into hydro- 
chloric acid. Ammonium chloride is obtained by simply 
evaporating the solution. It is purified by sublimation in 
stoneware pots which are heated in a furnace out of which the 
upper parts of the pots project. There the volatilized chloride 
condenses, and the sublimed product is known in commerce as 
sal ammoniac, or muriate of ammonia. 

It generally occurs as white or grayish, compact masses, 
having a crystalline fibrous structure. Its taste is sharp and 
salty. It dissolves in two and a half parts of cold, and in its 
own weight of boiling water. It is deposited from a satu- 
rated solution in small octahedra, grouped together in needles, 
and presenting a fern-leaf-like appearance. At a high tem- 
perature it volatilizes without melting j its vapor is dissociated, 
but the resulting NH^ and HCl at once recombine on cooling. 

Ammonium chloride is formed by the union of equal vol- 
umes of hydrochloric acid and ammonia gases. 



AMMONIUM HYDROSULPHIDE AND AMMONIUM SULPHIDE. 157 

AMMONIUM HYDROSULPHIDE AND AMMONIUM 
SULPHIDE. 

Hydrogen sulphide and ammonia gases unite in the cold 
in two different proportions, forming two compounds, ammo- 
nium hydrosulphide and ammonium sulphide. 



H^S -{- NH^ = ^^'1 

gen sulphide. Ammonia. Ammonium hydi 

[2 vol.) (2 vol.) 

ffS + 2NH» = ™;} 



Hydrogen sulphide. Ammonia. Ammonium sulphide. 

(2 vol.) (4 vol.) 

These compounds are definite, but are decomposed into their 
elements by heat. Horstmann and Salet have shown that hy- 
drogen sulphide and ammonia gases may be mixed in all pro- 
portions without contraction in volume taking place, provided 
the temperature be maintained above 60°. 

Ammonium hydrosulphide is generally obtained in solution 
by saturating aqueous ammonia with hydrogen sulphide. This 
solution is colorless, but acquires a yellow color on exposure to 
the air. When a quantity of ammonia is added to it equal to 
that which it already contains, ammonium sulphide, (NH*)^S, 
is formed, which corresponds to potassium sulphide, K^S. 

Ammonium sulphide is largely employed in the laboratory 
as a reagent for the detection of certain metals. 

If ammonium sulphide be added to a solution of ferrous 
sulphate, a double decomposition takes place ; ammonium sul- 
phate is formed and remains in solution, while ferrous sulphide 
forms a black precipitate. 

FeSO* + (NHO^S = FeS + (NH*).2S0* 

Ferrous sulphate. Ferrous sulphide. Ammonium sulphate. 

The salts of zinc, manganese, cobalt, and nickel are likewise 
precipitated as sulphides by ammonium sulphide. 

The salts of aluminium and chromium are precipitated as 
hydroxides, hydrogen sulphide being disengaged. 

The preceding salts are not precipitated by hydrogen sul- 
phide (the zinc salts are not precipitated if they be acid), but 
the latter reagent precipitates in the form of sulphides the salts 
of lead, bismuth, copper, cadmium, mercury, silver, antimony, 
tin, gold, and platinum. The sulphides of the latter four 
metals dissolve in an excess of ammonium sulphide. 

U 



158 ELEMENTS OF MODERN CHEMISTRY. 

The sulphides of arsenic, tin, antimony, gold, and platinum 
all form compounds with ammonium sulphide, in which the 
latter plays the part of a base. 

AMMONIUM NITRATE. 

(NH^)N03 

Ammonium nitrate is prepared by saturating nitric acid 
with ammonia. It crystallizes in large, transparent, fusible 
prisms, which are very soluble in water and produce a notable 
depression of temperature in the act of solution, extending 
even to — 15°. At 300° ammonium nitrate is decomposed 
into nitrogen monoxide and water. It is used for the prepa- 
ration of nitrous oxide, much used as an anaesthetic. 

AMMONIUM CARBONATE. 

When dry carbon dioxide and ammonia gases are mixed in 
the proportion of 2 volumes of the first to 4 volumes of the 
second, they condense, forming a white powder, which is am- 
monium carbamate, a compound which was formerly called 
anhydrous carbonate of ammonia. 

C0= + 2Nff = CO<^^g, 

Ammonium carbamate. 

The ammonium carbonate of commerce is generally consid- 
ered as a sesquicarbonate. It contains 2[C0'(NH*)^] -|- CO^ -)- 
2H^0. It is obtained by heating a mixture of equal parts of 
ammonium sulphate and chalk in a subliming apparatus. 
Ammonia and water are disengaged, and the sesquicarbonate 
of ammonium sublimes. 

Recently sublimed ammonium sesquicarbonate is transparent 
and crystalline. It has a strong ammoniacal odor and a sharp 
caustic taste. When exposed to the air it gradually loses 
ammonia and is converted into ammonium acid carbonate. 

Ammonium Acid Carbonate. — This salt, which is com- 
monly known as bicarbonate of ammonia, may be obtained by 
passing a current of carbonic acid gas into aqueous ammonia, 
to saturation. The acid salt separates in right rhombic prisms. 
The neutral carbonate of ammonium crystallizes from a cooled 
solution of the sesquicarbonate in ammonia-water. These salts 
present the following relations to the hypothetical carbonic acid : 



AMMONIUM SULPHATE — HYDROXYLAMINE. 159 



co<0| 


pf. ONH* 

CO<QJJ 




Carbonic acid. 


Ammonium acid 


Ammonium 


(Hypothetical.) 


carbonate. 


carbonate. 



AMMONIUM SULPHATE. 

(NH4)2S04 

This salt is obtained in the arts by passing the ammonia 
that is disengaged when gas-liquor is heated with lime into 
dilute sulphuric acid. It crystallizes in right rhombic prisms. 

It is colorless and has a sharp taste. It dissolves in two 
parts of cold, and in its own weight of boiling, water. It is 
insoluble in alcohol. 

Ammonium sulphate is manufactured on an enormous scale, 
and is used as a fertilizer and for the preparation of other 
ammonium compounds. 

HYDROXYLAMINE.^ 

NH2(0H) 

This remarkable compound was discovered by Lossen in 1865, 
and first obtained in a state of purity by Lobry de Bruyn in 1891. It 
is produced by the action of nascent hydrogen^that is, hydrogen at 
the instant when it is set free — upon nitric oxide, nitric acid, and 
certain nitrates. 

NO + 3H^ = 2NH2(OH) 
HNO^ + 3H2 == NH'^(OH) + 2H20 

When a current of nitric oxide is passed into a mixture of tin and 
hydrochloric acid, the hydroxylamine formed remains in solution 
combined with an excess of the acid. 

A more convenient method of preparation consists in adding a 
concentrated cold solution of sodium nitrite to one of sodium acid 
sulphite, and heating the resulting compound — sodium hydroxylamine 
disulphonate, N(OH)(SO^IS'a)^ — with water at 130° in closed vessels. 
The products are hydroxylamine, sulphuric acid, and sodium sul- 
phate. 

NalSr02 + 2NaHS0^ = N(0H)(S0=^Na)2 + NaOH 
2N(OH)(S03Na)2 + 4:W0 ^ (NH=«0H)2S0* + H^SO* + 2Na2SO* 

The sulphate of hydroxylamine is thus obtained. Hydroxylamine 
is an energetic base which, like ammonia, forms definite salts with 
the acids. It may be regarded as ammonia, in which the group OH 
(hydroxyl) has been substituted for one atom of hydrogen. 

The free base has been prepared by the action of sodium methox- 
ide (page 486) upon hydroxylamine hydrochloride dissolved in 
methyl alcohol. 

NH3(0H)C1 + NaOCH^ = NH2(0H) + NaCl + CH^OH 

Hydroxylamine Sodium Methyl 

hydrochloride. methoxide. alcohol. 

1 An amine is a compound representing NH^ in which one or more 
atoms of H are replaced by equivalent atoms or groups. 



160 ELEMENTS OF MODERN CHEMISTRY. 

Hydroxylamine is an odorless and colorless solid, crystallizing in 
plates or needles which deliquesce on exposure to the air. Its den- 
sity is 1.35. It melts at 33°, and boils at 58° under 22 mm. pressure. 
Heated above 100° it explodes violently. 

Its aqueous solution has powerful reducing properties : it pre- 
cipitates gold and mercury from solutions of their salts, and, on 
boiling with a cupric salt, throws down red cuprous oxide. 

HYDRAZINE. 

NH2— NH2 

By warming triazoacetic acid (CHN'^ — COOH)^ with sulphuric 
acid, Curtius obtained the sulphate of a new compound of hydrogen 
and nitrogen, (NH2)^==H2N — NH^, which is named hydrazine. 
This base forms a dihydrochloride (NH2)22HC1, and a hydrochloride 
(NH2)2HC1, both of which are crystallizable solids. 

Hydrazine hydrate, (NH^j^.H^O, is prepared by distilling the 
hydrochloride with potassium hydroxide. It is a fuming, caustic 
liquid, of peculiar odor, and boils at 119°. It destroys cork and 
caoutchouc, and even corrodes glass. The free base, (NH^)^, is ob- 
tained by treating the hydrate with an excess of barium oxide and 
distilling in vacuo. It is a fuming, inflammable liquid, which boils 
at 112.5° (Lobry de Bruyn). 

HYDRAZOIC ACID. 
HN3 

Curtius has isolated a remarkable compound of the composition 
N^H, which closely resembles hydrochloric acid in its properties. 
It is called hydrazoic acid. Its sodium salt is readily obtained by 
passing nitrous oxide over heated sodium amide (W. Wislicenus). 

2NaNH2 4- WO = NaN^ + NaOH + NH» 

Sodium amide. Sodium hydrazoate. 

An aqueous solution of the free acid may be prepared by treating 
this sodium salt with dilute sulphuric acid, or by conducting red 
nitrous vapors into a solution of hydrazine hydrate at 0°. 

Hydrazoic acid is a colorless, mobile liquid, having a very pene- 
trating odor. Its boiling point is 87°. Its solution is strongly acid. 
It dissolves many metals with evolution of hydrogen. The result- 
ing hydrazoates are in many respects analogous to the chlorides. 
Silver hydrazoate forms a white curdy precipitate. 

Hydrazoic acid and many of its salts are explosive. 

OXYGEN COMPOUNDS OF NITROaEN. 

Five compounds of nitrogen and oxygen are known. 

comJosTtI'on. volumetric composition. 

Nitrous oxide N^O 2 vol. N and 1 v. condensed in 2 v. 

Nitric oxide NO 1 vol. N and 1 v. = 2 v. 

Nitrogen trioxide .... N^O'' 2 vol. N and 3 v. condensed in 2 v. 
Nitrogen peroxide . NO^ and N^O* 2 vol. N and 4 v. condensed in 2 v. 
Nitrogen pentoxide . . . . N^O^ 2 vol. N and 6 v. condensed in 2 v. 



NITROGEN MONOXIDE. 



161 



Nitrogen trioxide and nitrogen pentoxide combine with 
water, forming nitrous and nitric acids. 

N^O' + R'O = 2HN02 
N205 _|. H=^0 = 2HN03 

NITROUS OXIDE. 

Density compared to air 1.527 

Density compared to hydrogen 22. 

Molecular weight N^O = 44. 

This gas, known also as protoxide or monoxide of nitrogen, 
and laughing-gas, was discovered by Priestley in 1776. 

Preparation. — It is obtained by gently heating ammonium 
nitrate in a glass retort. The salt melts, and then decomposes 




Fig. 61. 

with effervescence into water and nitrous oxide, which may 
be collected over water (Fig. 61). 

(NH^NO^ = ^'0 + 2H'0 

Properties. — Nitrous oxide is colorless and odorless, but 
possesses a sweetish taste. It is not permanent, and may 
be liquefied by strong pressure. It is liquefied on a consider- 
able scale at present, that it may be transported in small bulk 
for the use of dentists. For this purpose it is compressed in 
strong iron reservoirs from which it may be easily drawn in 
the liquid state for experiments after first cooling the reser- 
voir in ice and salt. 

A remarkable experiment can be performed as follows : A 
quantity of liquid nitrous oxide is poured into a test-tube 
fixed by a cork in the neck of a bottle ; a portion of it 
instantly volatilizes, producing intense cold. If now a little 
mercury be pou.red into the tube, it will sink through the 
liquid monoxide and immediately be solidified. A small piece 
I 14* 



162 



ELEMENTS OF MODERN CHEMISTRY. 



of incandescent charcoal let fall into the tube will float upon 
the surface of the liquid, and burn with great brilliancy, not- 
withstanding the intense cold by 
which it is surrounded, as evi- 
denced by the freezing of the 
mercury (Fig. 62). 

Water dissolves about its own 
volume of nitrous oxide at ordi- 




nary temperatures. 

A taper which has been extin- 
guished, but still bears a spark 
of fire, is relighted, and burns 
Fig 62 brilliantly when plunged into a 

jar of nitrous oxide (Fig. 63). 
In the same manner, the combustion of sulphur and phos- 
phorus is effected with great 
energy in an atmosphere of 
this gas. 

Equal volumes of nitrous 
oxide and hydrogen form a 
mixture which explodes on 
the passage of an electric 
spark or on the application 
of flame. 




N^O + H^ =r H^O + N^ 

2 2 2 2 

volumes, voluraes. volumes, volumes. 

Respiration is a slow com- 
bustion and may be sustained 
for a few seconds by nitrous 
oxide. Such inhalation 
does not suffocate but it dis- 
turbs the functions of the 
jPjQ gg nervous system, producing 

anaesthesia, and for this pur- 
pose nitrous oxide is now largely employed by surgeons and 
dentists. The insensibility is frequently preceded by a stage 
of intoxication, hence the name laughing-gas, which was given 
by Davy. 

It must be added that these exhilarating effects have not 
been observed in recent experiments with perfectly pure 
nitrous oxide. 



NITRIC OXIDE. 



163 



NITRIC OXIDE. 

Density compared to air 1.039 

Density compared to hydrogen 15. 

Molecular weight NO =30. 

Preparation. — This gas was discovered in 1772 by Hales ; 
it is prepared by decomposing cold, dilute nitric acid by metallic 
copper. 

3Cii + 8HN0^ = 3Cu(NO')2 + 4:W0 + 2N0 

Copper. Nitric acid. Cupric nitrate. 

The copper and water are introduced into a gas-bottle, and 
ordinary nitric acid is added by means of a funnel-tube ; the 
copper is immediately attacked and dissolved, forming cupric 
nitrate (Fig. 64), and at the same time nitric oxide gas is dis- 
engaged. This gas absorbs oxygen from the air and is con- 




FiG. 64. 

verted into red vapors, which are at first apparent in the gas- 
bottle, but as the evolution of nitric oxide continues, the gas 
in the flask gradually becomes colorless, and may then be col- 
lected in jars over water. 

Properties. — Nitric oxide is a colorless gas. Its liquefaction 
was first effected by Cailletet. It is decomposable by heat, but 
less easily than the monoxide. It is scarcely soluble in water, 
which only takes up a twentieth of its volume. Its most charac- 
teristic property is the energy with which it absorbs half its 
volume of oxygen, passing into the state of nitrogen peroxide 
or red vapors. 



164 ELEMENTS OF MODERN CHEMISTRY. 

If a jar filled with nitric oxide be opened to the air, the red 
vapors appear at once. 

2N0 + 0^ = N^O* 

Nitric oxide supports the combustion of certain substances. 
Phosphorus burns in it brilliantly, but the gas does not, like 
oxygen and nitrogen monoxide, relight a taper still presenting 
a spark. 

Hydrogen decomposes nitric oxide at a temperature but 
slightly elevated, forming water and nitrogen. 

NO + H^ = N + H^O 

The mixture of the two gases in equal volumes takes fire on 
the application of flame. 

If a few drops of carbon disulphide be poured into a jar of 
nitric oxide, the vapor of the volatile liquid is at once difixised 
throughout the gas, and on the approach of a lighted taper a 
brilliant flash of light is produced, the sulphur and carbon being 
burned by the oxygen of the nitric oxide. 

The light produced by this combustion is rich in actinic rays : 
like the solar light, it efi"ects the explosive combination of 
chlorine and hydrogen. 

When a mixture of nitric oxide with an excess of hydrogen 
is passed through a heated tube containing platinum sponge, 
water and ammonia are formed. 

NO + 5H = ff + NH=^ 

Under other circumstances hydroxylamine may be produced. 

A solution of ferrous sulphate absorbs nitric oxide with 
avidity, assuming a dark-brown color ; this is a characteristic 
property, by which nitric oxide may be recognized. 

NITROGEN THIOXIDE. 

N203 

This compound does not appear to exist except at very 
low temperatures. It is formed by passing nitric oxide into 
liquid nitrogen peroxide at — 21°. 

2N0 + N==0* = 2N20' 

It is a blue liquid, which congeals at — 82°, and boils, 
with decomposition, at 3.5°. Even below this temperature 
the liquid appears to sufi"er partial decomposition. 



NITROGEN PEROXIDE. 



165 



NITROGEN PEROXIDE. 

NO^ or N'-^O* 
Preparation. — When well dried lead nitrate is heated to 
redness it is decomposed into lead oxide and nitrogen peroxide, 
which may be condensed in a well-cooled receiver. 



Pb(NO^)^ 

Lead nitrate. 



= PbO + 

Lead oxide. 



+ N^O^ 



The first portions of nitrogen peroxide that are condensed 
generally retain a trace of moisture, and present a green color ; 
if the receiver be then changed, there collects a yellow liquid 
which solidifies to a crystalline mass at — 10°. 

Properties. — Nitrogen peroxide is a mobile liquid, almost 
colorless at very low temperatures ; at 0° it has a somewhat 
darker color, and at 15° it is orange-brown. It boils at 22°, 
and its vapor is red. Near the point of ebullition its volu- 
metric composition corresponds to the formula N^O* ; that is, 
two volumes of nitrogen and four volumes of oxygen are con- 
densed into two volumes of N^O*, and occupy the same space 
as two atoms (one molecule) of hydrogen. 

But at a higher temperature this vapor is dissociated ; that 
is, it is gradually decomposed in such a manner as to occupy 
double its primitive volume. The two atoms of nitrogen and 
four atoms of oxygen which constitute two volumes of N^O* 
at° a low temperature, occupy four volumes at about 140°. 



NO^ 


NO^ 



N 


0^ 


N 


0^ 



Red vapors at 20°. 



Eed vapors at 140°. 



The vapor of nitrogen peroxide is very corrosive, and dan- 
gerous to inhale. 

A small quantity of cold water decomposes nitrogen perox- 
ide into nitrogen trioxide and nitric acid ; a larger quantity of 
water causes the formation of nitrous and nitric acids. 
N^O* _|_ H^o = HNO^ -f HNO^ 

Nitrous acid. Nitric acid. 

At ordinary temperatures and in presence of much water, 
nitric oxide is formed. 

3N0^ + H^O = 2HN0^ -f NO 



166 ELEMENTS OF MODERN CHEMISTRY. 

When a mixture of nitrogen peroxide and hydrogen is passed 
over heated platinum sponge, water and ammonia are formed. 

Certain very finely divided metals, especially copper, nickel, 
and cobalt, have the property of absorbing large quantities of 
nitrogen peroxide, apparently combining with it to form definite 
compounds that have been named nitro-metals. The copper 
compound, Cu^NO^ is a dark-brown powder, which is decom- 
posed at 90°, and also by water, into copper and nitrogen 
peroxide. 

Nitryl Chloride and Bromide.— Like nitric oxide, which 
may be called nitrosyl, nitrogen peroxide may play the part of 
a radical. There exists a chloride and also a bromide of nitro- 
gen peroxide or nitryl. 

NO'Cl NO'Br 

Nitryl chloride. Nitryl bromide. 

The latter compound is formed, together with other products, 
when bromine acts upon nitrogen peroxide at a very low tem- 
perature. The chloride of nitryl has recently been obtained 
by the reaction of phosphorus oxychloride upon silver nitrate. 

POCP -f 3AgN0' = AgTO* -f 3(N0'C1) 

Phosphorus Silver nitrate. Silver phosphate. Nitryl chloride, 

oxychloride. 

Nitryl chloride is a light-yellow liquid, boiling at -}-5° and 
solidifying at — 31°. 

In contact with water, it forms nitryl hydrate (nitric acid), 
and hydrochloric acid. 

NO^Cl + H^O = HCl + NOIOH 

The nitric acid is formed at the expense of the water, of 
which one atom of hydrogen is removed by the chlorine and 
replaced by the radical! nitryl. Hence in nitric acid the group 
NO^ replaces one atom of hydrogen in water; this group is 
therefore monatomic. 

But the atom of hydrogen in nitric acid may also be replaced 
by another nitryl group, and the result is an oxide of nitryl, 
the anhydride of nitric acid, or nitrogen pentoxide. The fol- 
lowing formulae will illustrate the relations between these com- 
pounds and water which is their type : 



H I " H I " N0\ 

Water. Nitric acid. Nitrogen pentoxide. 

(Nitryl hydrate.) (Nitryl oxide.) 



NITROGEN PENTOXIDE — NITRIC ACID. 167 

NITROaEN PENTOXIDE. 

(nitric anhydride.) 

This compound was obtained by H. Sainte-Claire Deville by 
the action of chlorine upon dry silver nitrate heated to between 
58 and 60°. 

2AgN0^ + CP = N^O^ + 2AgCl + 

Silver nitrate. Nitrogen pentoxide. Silver chloride. 

It may also be obtained by passing the vapor of nitryl chlo- 
ride over silver nitrate heated to 70°. 

AgO.NO^ + NO^Cl = AgCl + (NOO^^O 

Silver nitrate. Nitryl chloride. Nitrogen pentoxide. 

Also, as shown by Berthelot, by the action of phosphorus 
pentoxide upon concentrated nitric acid. 

2HN0^ — H^O = N^O^ 

Nitrogen pentoxide is solid and crystallizes in right-rhombic 
prisms. It melts at 29.5°, and boils between 48 and 50°. It 
is very unstable and explodes spontaneously even when it is 
preserved at a low temperature. 

NITRIC ACID. 
HN03 

The atmosphere frequently contains a trace of nitric acid 
vapor or other compounds of nitrogen and oxygen, and small 
quantities of ammonium nitrate and nitrite may be detected in 
rain-water. After passing a current of air for a long time 
through a solution of potassium carbonate, the liquid is found 
to contain potassium nitrate (Cloez). It may be admitted that 
the compounds of nitrogen and oxygen are formed directly by 
the action of electricity upon the elements of the air. 

The nitrates of potassium, sodium, magnesium, and calcium 
are met with in certain soils, often in abundance. They are 
formed wherever nitrogenized organic matters decompose in 
contact with the air and in presence of porous matters and 
alkaline bases. 

By the activity of peculiar micro-organisms, ammonia and 
ammonium nitrite are first produced, and these are oxidized 



168 



ELEMENTS OF MODERN CHEMISTRY. 



and converted into nitrates. In rainless regions these nitrates 
form extensive deposits. 

Preparation. — Nitric acid is obtained by decomposing an 
alkaline nitrate with sulphuric acid. In the laboratory, the 
operation may be conducted in a glass retort, the neck of which 
passes, without cork, into a cooled receiver. 98 parts of con- 
centrated sulphuric acid and 85 parts of sodium nitrate are 
employed. On the application of heat, nitric acid is vola- 
tilized, mixed at the commencement of the operation with red 
vapors. The acid condenses in the receiver as a yellow liquid, 
fuming in the air. Sodium acid sulphate remains in the retort. 



H^SO* + NaNO^ = 



Sodium nitrate. Sodium acid sulphate. 

In the arts, the sodium nitrate is decomposed with a less 
concentrated sulphuric acid, the decomposition, of the nitric 
acid during the operation being thus avoided. The operation 
is conducted in cast-iron retorts, A (Fig. 65), the lateral tubes 
of which, B, are adapted to stoneware tubes communicating 
JHL ,-C\, 




with a series of stoneware bottles, D, where the acid condenses. 
The temperature is elevated towards the close of the operation, 
and sodium neutral sulphate is formed. 

H^SO* -f 2NaN0^ == Na^SO* + 2HN0^ 
Properties. — When perfectly pure, nitric acid is colorless, 
but it rapidly becomes yellow under the influence of light, 
undergoing a partial decomposition. When exposed to the 



NITRIC ACID. 169 

air, it gives off abundant white fiimes. Its. density is 1.52 ; it 
solidifies at — 49°, and boils at 86°. 

Wben its vapor is passed tbrougb a red-hot porcelain tube, 
t is decomposed into nitrogen peroxide, oxygen, and water. 

2HN0^ = WO + N^O* + 

The same decomposition takes place when the concentrated 
acid is boiled under ordinary pressures : its boiling-point gradu- 
ally rises while the acid becomes weaker until a temperature of 
120.5° is reached. The residual liquid, which distils without 
further decomposition, contains 68 per cent, of the acid and has 
a density of 1.414. The same acid results when a weaker acid 
is distilled ; it becomes gradually stronger until a boiling-point 
of 120.5° is attained. However, the acid which distils at a 
temperature higher than 86° cannot be considered a definite 
hydrate ; its composition depends on the pressure. 

Nitric acid readily gives up a portion of its oxygen to bodies 
having an afiinity for that element. It energetically oxidizes 
sulphur, phosphorus, arsenic, iodine, silicon, carbon, and most 
of the metals. 

If nitric acid be poured upon red-hot charcoal, the combus- 
tion is vividly intensified by the decomposition of the nitric 
acid, and red fumes appear at the same time. 

Copper decomposes nitric acid with an abundant disengage- 
ment of nitric oxide, which is converted into nitrogen peroxide 
by contact with the air. 

If dilute nitric acid be poured upon clean iron wire, chemi^ 
cal action at once takes place, and there is an abundant evolu- 
tion of red vapor ; but if the same wire be plunged into the 
concentrated acid, no action is manifested ; and further, if the 
strong acid be poured off and replaced by dilute acid, the latter 
undergoes no decomposition; the iron has become passive hj 
becoming covered with a thin film of oxide of iron. This 
passive state of iron may also be brought about by means of 
other oxidizing agents, such as chromic and chloric acids. 

The action of tin upon nitric acid is worthy of notice. Tor- 
rents of red vapor are disengaged, and the metal is converted 
into a white powder, which is stannic acid. In this reaction 
small quantities of ammonia and hydroxylamine are formed at 
the expense of the elements of the nitric acid, and remain 
combined with the excess of acid. 

The conversion of nitric acid into ammonia may be more 
B 15 



170 ELEMENTS OF MODERN CHEMISTRY. 

complete. If zinc be introduced into very dilute nitric acid, 
the metal dissolves slowly and without disengagement of gas ; 
the liquid is then found to contain zinc nitrate and ammo- 
nium nitrate. The nascent hydrogen set free from a portion 
of the nitric acid by the zinc reduces another portion of the 
■acid, forming water and ammonia. 

Zn -f 2HN0=^ = Zn(NO^)^ + H^ 

Zinc. Zinc nitrate. 

2HN0^ + 4:W = 3H^0 + (NH*)NO' 

Ammonium nitrate. 

Nitric oxide decomposes nitric acid. The acid is reduced, 
and either nitrogen peroxide or nitrous acid is formed and 
remains dissolved in the liquid, the former communicating a 
brown, the second a blue or green color. 

Nitric acid is one of the most important acids. It is em- 
ployed in the manufacture of sulphuric acid, and also to oxidize 
certain organic matters, such as starch and sugar, which it 
converts into oxalic acid. It is also used in parting gold, in 
the manufacture of nitrates, nitroglycerin, picric acid, and coal- 
tar colors, and is the most generally useful oxidizing agent in 
the laboratory. 

Nitro-hydrocMoric Acid. — A mixture of nitric and hydro- 
chloric acids is called nitro-hydrochloric or nitro- muriatic acid, 
or aqua regia. This liquid dissolves gold and platinum, and 
it owes this property to the chlorine, which is set at liberty by 
the mutual action of the two acids. 

6HC1 + 2HN0^ = 4ff + 2N0 + 3CP 

When the mixture is left to itself it gradually assumes a 
yellow color, undergoing a partial decomposition. But this 
decomposition is limited, and only complete in the presence 
of metals which are capable of absorbing free chlorine. 

The reaction between hydrochloric and nitric acids gives 
rise to the formation of another product, consisting of oxy- 
gen, nitrogen, and chlorine. It is nitrosyl chloride^ NO. CI. 

3HC1 + HNO^ = 2W0 -f NOCl + CP 

Nitrosyl chloride is an orange-colored gas which, with the 
aid of a freezing mixture, is readily condensed to a liquid 
of the same color. This boils at — 5°. By reacting with 
water nitrosyl chloride forms hydrochloric and nitrous acids. 

No.ci -f WO = Hci 4- no.oh; 



PHOSPHORUS. 171 

Similarly a chloride and a nitrite result when nitrosyl 
chloride is treated with an alkaline hydroxide. 

NO.Cl + 2K0H = KCl + NO.OK + ffO 

It will be noticed that nitrosyl chloride bears tl^e same rela- 
tion to nitrous acid that nitryl chloride bears to nitric acid. 
The following formulae will illustrate the constitution of these 
bodies : 

N0.C1 NO}, NO}, 

Nitrosyl chloride. Nitrous acid. Nitrogen trioxide. 

NOICI NO^JO ^%\0 

Nitryl chloride. Nitric acid. Nitrogen pentoxide. 



PHOSPHOKUS. 

Vapor density compared to air 4.32 

Vapor density compared to hydrogen .... 61.1 
Atomic weight P = 30.75 

Brand, an alchemist of Hamburg, while attempting to ex- 
tract the philosopher's stone from urine, discovered phosphorus 
in 1669. But urine contains only a small quantity of phos- 
phates and can yield but traces of phosphorus, so that this 
body only became generally known to chemists after G-ahn 
demonstrated its existence in bones, and Scheele discovered the 
process for its extraction. 

The process of the latter chemist is still in use ; it consists 
in treating bone-ash with dilute sulphuric acid, by which means 
the tricalcium phosphate of the bones is converted into mono- 
calcium phosphate, ordinarily called acid phosphate of lime. 

Ca^(PO*)' + 2H^S0* = CsiW(POy + 2CaS0* 

Tricalcium Calcium acid Calcium 

phosphate. phosphate. sulphate. 

The latter phosphate being soluble is separated from the 
calcium sulphate by filtration, and the solution is evaporated 
and mixed with powdered charcoal. The mixture is dried and 
gradually heated to redness in cast-iron vessels. By this means 
the calcium acid phosphate is converted into calcium meta- 
phosphate by the expulsion of two molecules of water. 

CaH*(PO*)' = 2H^0 -f Ca(PO^)^ 

Calcium acid phosphate. Calcium metaphosphate. 



172 



ELEMENTS OF MODERN CHEMISTRY. 



The latter is strongly heated with charcoal in clay retorts 
(Fig. 66), and is decomposed, yielding carbon monoxide and 
phosphorus which distils over, and leaving a residue of calcium 
pyrophosphate. 

2Ca(PO^)2 -f 5C = CaT^O^ + 5C0 -h F 



Calcium 
metaphosphate. 



Calcium 
pyrcpliospbate. 



+ SCO + 

Carbon 
monoxide. 



The phosphorus condenses in the water in the receiver A, 
in which the neck of the retort C is engaged. 




Fig. 66. 



The crude product is purified either by redistilling it, or 
by enclosing it in a chamois-skin sack and strongly com- 
pressing it under water at 50° ; the phosphorus passes through 
the leather and collects under the water. It is moulded into 
sticks by being drawn up into slightly conical glass tubes, 
which are then plunged into cold water. The phosphorus 
solidifies and is easily drawn from the tubes. 

A newer process of manufacturing phosphorus consists in directly 
reducing the calcium phosphate by charcoal at the high tempera- 
tures attainable in the electric furnace (page 210). A flux is added 
to form a liquid slag with the lime, which remains in the furnace 
while the phosphorus distils. 

Physical Properties. — Recently-fused phosphorus is trans- 
parent, colorless, or having a pale-yellow tint, flexiblCj and soft 



PHOSPHORUS. 173 

enough to be easily scratclied by the nail. One-tenth per cent, 
of sulphur renders it hard and brittle. It has a well-marked 
odor, slightly resembling that of garlic. Its density at 10° is 
1.83. It melts at -4-1° and boils at 290° ; its vapor is colorless 
and has a density of -1.32 compared to air, or 61.1 compared 
to hydrogen. 

If one volume of hydrogen weighs 1, one volume of vapor 
of phosphorus weighs 61.1, and this number should represent 
the weight of one atom of phosphorus ; now it represents the 
weight of two atoms, and the vapor of phosphorus presents 
the "singular anomaly that it contains in the same volume 
twice as many atoms as the simple gases, such as hydrogen 
or nitrogen. If one volume of hydrogen contain one atom, 
one volume of phosphorus vapor contains two. It has been 
found, however, that at temperatures considerably above 
1000° the density of phosphorus vapor is diminished : the 
molecules consisting of four atoms are dissociated into simpler 
ones. 

p4 __ 2P2 

The vapor density of arsenic is likewise anomalous, corre- 
sponding to the molecular formula As*. 

Phosphorus volatilizes below its boiling-point and even below 
its melting-point. At ordinary temperatures it emits vapors in 
a vacuum and even in the air. It is luminous in the dark, 
from which property it derives its name, which signifies light- 
bearer. The cause of this phenomenon is still obscure, but is 
generally attributed to the slow oxidation which phosphorus 
undergoes in the air. 

When a stick of transparent phosphorus is kept under water, 
it gradually becomes opaque and covered with a yellowish- white 
pulverulent powder, while the central parts retain their trans- 
parence. This white phosphorus is still pure, but the surface 
of the stick has divided into a multitude of little particles which 
present a crystalline appearance. Some of them become de- 
tached and remain suspended in the water, giving to the latter 
the property of being luminous in the dark. 

Phosphorus is rapidly dissolved by carbon disulphide and is 
deposited in rhombic dodecahedra on the slow evaporation of 
the solution. 

There is an amorphous variety of phosphorus which difi'ers 
so much from ordinary phosphorus that it presents the prop- 

16* 



174 ELEMENTS OF MODERN CHEMISTRY. 

erties of an entirely different substance. It has a dark brown- 
red color, and is not luminous in tbe dark. It is insoluble in 
carbon disulphide ; it does not melt and take fire like ordi- 
nary phosphorus when heated to 60°. It is amorphous, and 
presents a conchoidal fracture. Its density is 2.14. Ordinary 
phosphorus is one of the most dangerous poisons, but this red 
body exerts no action upon the economy. At 260° amorphous 
phosphorus melts and again becomes ordinary phosphorus. 

Amorphous phosphorus results from a physical change 
brought about by the action of light or heat on the ordinary 
variety. If a stick of phosphorus be exposed to direct sun- 
light, its surface assumes a red color ; or if it be maintained 
for a long time at a temperature of 240°, it is entirely con- 
verted into the amorphous variety. 

This transformation is also accomplished by the influence of 
certain chemical agents. If a small stick of ordinary phos- 
phorus be introduced into a test-tube and a very minute por- 
tion of iodine be allowed to fall upon it, the iodine unites with 
the phosphorus with the production of light and heat. A trace 
of phosphorus iodide is formed, and the remainder of the phos- 
phorus is converted into a hard, black mass, which yields a red 
powder ; this is amorphous phosphorus (E. Kopp, Brodie). 

Thus prepared, this body volatilizes like arsenic, without 
melting, and can be distilled without alteration, condensing in 
a black mass, which contains only traces of iodine. 

Chemical Properties. — Ordinary phosphorus possesses a 
strong affinity for oxygen. When exposed to the air it slowly 
oxidizes, and the slow combustion, aided by the moisture of the 
air, produces a mixture of phosphorous and phosphoric acids. 
Schbnbein has shown that the slow oxidation of phosphorus is 
accompanied by the formation of small quantities of ozone and 
hydrogen dioxide. 

WHen heated in the air to a temperature of 60°, phosphorus 
takes fire and burns, producing a bright light and white vapors 
of phosphorus pentoxide mixed with some phosphorus trioxide. 
In oxygen the combustion takes place with great brilliancy. It 
is remarkable that under ordinary pressures phosphorus will not 
burn in pure and dry oxygen : it can be melted and even dis- 
tilled in such an atmosphere (Dixon). 

Phosphorus may be burned under warm water by passing a 
current of oxygen through the melted element by means of a 
tube drawn out to a point (Fig. 67) ; each bubble of oxygen 



HYDROGEN PHOSPHIDE. 



175 



wMcli comes in contact with the phosphorus produces a bright 
flash. 

Phosphorus takes fire spontaneously in an atmosphere of dry 
chlorine, phosphorus pentachloride being produced. 

Uses of Phosphorus. — This body is principally employed in 
the manufacture of matches. The inflammable tips of friction- 
matches contain either ordinary or amorphous phosphorus. In 
the first case, the phosphorus is mixed with inert substances, 
such as sand or ochre, held together by strong glue ; in the 




Fig. 67. 

second case, the ignition of the amorphous phosphorus, which 
is but slightly combustible, is determined by potassium chlorate, 
to which is also added antimony sulphide. All of these sub- 
stances are made into a paste, into which the ends of the 
matches are dipped. Sometimes the match-sticks are tipped 
with a paste composed of potassium chlorate and antimony 
sulphide, a mixture which only takes fire by friction upon a 
prepared surface, composed generally of amorphous phosphorus 
and antimony sulphide. All of these mixtures are held to- 
gether by strong glue. 

HYDROGEN PHOSPHIDE (PHOSPHIJ^E). 

Density compared to air 1.178 

Density compared to hydrogen 17. 

Molecular weight PH^ =34. 

This gas was discovered by Gengembre in 1783. 

When phosphorus is heated with a solution of caustic potash, 
there is a gas disengaged, which inflames spontaneously on con- 
tact with the air ; this is hydrogen phosphide. It is formed 
according to the following equation : 

3K0H -f 4P + SH^O = SKHTO^ + PH^ 

Potassium hydrate. Potassium hypophosphite. 



176 



ELEMENTS OF MODERN CHEMISTRY. 



Preparation. — 1. Hydrogen phosphide may be prepared by 
heating phosphorus with a strong solution of potassium hydrate, 
or with thick milk of lime, with which the flask (Fig. 68) 




Fig. 68. 

should be almost entirely filled. The gas is conducted under 
the surface of water, and as each bubble arrives in contact with 
the air it takes fire spontaneously, producing a bright flash and 
a wreath of white smoke, which enlarges as it rises in the air. 

2. The same spontaneously inflammable gas is evolved when 
calcium phosphide is thrown into water (Fig. 69). The phos- 
phide of calcium is prepared by passing vapor of phosphorus 
over fragments of incandescent lime ; it instantly decomposes 
water with formation of calcium hypophosphite and sponta- 
neously inflammable hydrogen phosphide. 

However, when calcium phosphide is treated with hydro- 
chloric acid, hydrogen phosphide is produced, which does not 
take fire without the application of heat (Fig. 70). 

In this case, the gas is formed by double decomposition 
between the hydrochloric acid and the calcium phosphide ; the 
calcium combines with the chlorine, forming calcium chloride, 
and the hydrogen of the acid combines with the phosphorus. 

3. In the same manner, when phosphorous acid is strongly 
heated in a small retort, it evolves a hydrogen phosphide which 
is not spontaneously inflammable. 



4H3PO^ : 

Phosphorous acid. 



PH^ -I- 3HT0* 

Phosphoric acid. 



COMPOUNDS OF PHOSPHORUS AND CHLORINE. 



177 



Properties. — The gas thus obtained is colorless, and pos- 
sesses a garlicky odor. It is but slightly soluble in water, but 
is soluble in alcohol and in ether. When it is pure it does not 
take fire in the air at a temperature below 100°, and then 
burns with a very luminous white flame. According to Paul 
Thenard, the spontaneous inflammability of the hydrogen phos- 
phide prepared by the methods first mentioned is due to the 





Fig. 69. 



Fig. 70. 



presence of another phosphide, P^H* ; this is a very volatile 
liquid, extremely inflammable, and the least trace of its vapor 
in hydrogen phosphide gas communicates to the latter the 
property of spontaneous inflammability. 

Hydrogen phosphide liquefies at about — 85°, and freezes at 
— 132.5° ; it is absorbed by a solution of cuprous chloride in hy- 
drochloric acid, with the formation of the compound CuClPH^. 

The composition of hydrogen phosphide, PH^, recalls that of 
ammonia, NH^, and the analogy between the two gases is further 
revealed by the property common to both of uniting with hydri- 
odic acid, PhospJionium iodide^ PHIHI or PH^I, is a well- 
defined solid body, crystallizing in brilliant tetragonal prisms. 
Caustic alkalies decompose it with formation of phosphine. 

The existence of a solid phosphide of hydrogen has been 
demonstrated, and the formula P'H attributed to it. 



COMPOUNDS OF PHOSPHORUS AND CHLORINE. 

There are two chlorides of phosphorus : 

Phosphorus trichloride PGP 

Phosphorus pentachloride PCI* 



178 ELEMENTS OP MODERN CHEMISTRY. 

There are, besides, 

Phosphorus oxychloride POCl^ 

Phosphorus sulphochloride PSCl^ 

PHOSPHOEUS THICHLORIDE. 
POP 

When a current of dry chlorine is passed over phosphorus 
heated in a small tubulated retort, a liquid compound of chlo- 
rine and phosphorus is formed and may be condensed in a 
cooled receiver. This is phosphorus trichloride. It is a 
fuming, colorless liquid, having a density of 1.61 and boiling 
at 76°. It solidifies at —112°. 

If it be poured into water, it at first sinks to the bottom, 
and then rapidly disappears, evolving white fumes of hydro- 
chloric acid, and forming phosphorous acid, which remains in 
solution. 

POP -f- 3H^0 = WFO' -f 3HC1 

PHOSPHORUS PENTACHLORIDE. 

PC15 

In contact with an excess of chlorine, phosphorus trichloride 
absorbs two more atoms of that gas, and condenses into a yellow 
crystalline solid, phosphorus pentaehloride. 

This body is volatile, and sublimes without fusion when 
heated, even below 100°. When heated under pressure, it 
melts at 148° and boils at a slightly higher temperature. Its 
vapor density, taken at 336° and reduced to 0°, is equal to 
3.656. This density should be double, supposing that the 
molecule PCP occupies two volumes. The anomaly, however, 
is only apparent, for there are good reasons for believing that 
at the temperature 336° the vapor of phosphorus pentaehloride 
no longer exists, and that the compound is decomposed or dis- 
sociated into a mixture of phosphorus trichloride and chlorine, 
a mixture which would give four volumes of vapor for one 
molecule of PCP. 

pp,5 f PCP = 2 volumes. 

^^^ ~ I CP = 2 volumes. 

4 volumes. 

Indeed, when the vapor density of phosphorus pentaehloride 
is taken by diflfusing it in the vapor of the protochloride, which 



PHOSPHORUS OXTCHLORIDE. 179 

prevents the dissociation before mentioned, a figure is found 
wliich corresponds very nearly with the theoretic density 7.21 
(A. Wurtz). 

Phosphorus pentachloride decomposes water with energy, 
forming hydrochloric and phosphoric acids. 

PCP + 4.W0 = HTO* + 5HC1 

When only a small quantity of water is present, hydrochloric 
acid is disengaged, by the exchange of two atoms of chlorine 
for one atom of oxygen, and a colorless liquid is formed which 
is called phosphorus oxychloride. When heated in a current 
of hydrogen sulphide, phosphorus pentachloride is converted 
into the sulphochloride, a colorless liquid boiling at 126°. 

PCP + H^O = 2HC1 + POCP 
PCP + H^S = 2HC1 + PSCP 



PHOSPHORUS OXYCHLORIDE. 

POCP 

This body is readily obtained by exposing phosphorus penta- 
chloride to moist air until it becomes liquid, and subsequently 
distilling the liquid (A. Wurtz). It is formed in a great num- 
ber of reactions when phosphorus pentachloride is heated with 
hydrated acids, such as oxalic acid, boric acid, etc., or with 
oxides, such as phosphoric oxide. In these cases, one atom of 
oxygen from the oxidized body is exchanged for two atoms of 
chlorine from the pentachloride (Grerhardt). 

Phosphorus oxychloride is a colorless liquid, boiling at 110°. 
When poured into water, it sinks and is at once decomposed, 
hydrochloric and phosphoric acids being formed. 

POCP + iajo^^: ^3J0^ + 3HC1 

Phosphorus oxychloride. 3 molecules water. Phosphoric acid. 

COMPOUNDS OF PHOSPHORUS WITH BROMINE 
AND IODINE. 

Two bromides of phosphorus are known : 
Phosphorus tribromide, PBr^, a colorless liquid. 
Phosphorus pentabromide, PBr^, a yellow, crystalline mass. 
To the trichloride and tribromide of phosphorus there cor 
responds a triiodide, concerning which but little is known. 



180 ELEMENTS OF MODERN CHEMISTRY. 

The best defined and most important combination of phos- 
phorus with iodine is the compound P^P. 

Phosphorus Iodide, PT.— This body is obtained by dis- 
solving dry phosphorus in carbon disulphide and gradually 
adding iodine to the solution. The liquor is distilled on the 
water-bath, and leaves a bright-red, crystalline mass. This 
is the iodide P'P. 

It crystallizes in long, brilliant, flexible needles, which melt 
at 110°. On contact with water it is decomposed, forming 
phosphorous and hydriodic acids. 

Phosphorus Fluorides. — A trifluoride, PF^, and a penta- 
fiuoride, PF^, are known. Both are colorless gases at ordi- 
nary temperatures. The pentafluoride is the only compound 
of pentavalent phosphorus which can exist as a gas without 
dissociation. It is stable at high temperatures. 

COMPOUNDS OF PHOSPHORUS AND OXYGEN. 

Phosphorus combines with oxygen, forming two oxides : 

Phosphorus trioxide, or phosphorous oxide . . P^O^ 
Phosphorus pentoxide, or phosphoric oxide . . P^QS 

Recent investigations by Thorpe and Tutton seem to phow 
that the products of the slow combustion of phosphorus con- 
tain also an oxide having the composition P^O"^, corresponding 
to nitrogen tetroxide. Both the trioxide and the pentoxide 
can combine with three molecules of water, phosphorous and 
phosphoric acids being thus formed. 

2P*0« + 6H20 = 4H3P03 

P205 + 3H20 r= 2H3P04 

Besides these two acids there is another containing less oxy- 
gen ; it is hypophosphorous acid, whose corresponding oxide is 
unknown. These three acids form a series containing for three 
atoms of hydrogen and one atom of phosphorus regularly-in- 
creasing quantities of oxygen ; they may be said to constitute 
different degrees of oxidation of hydrogen phosphide. 

PH3 hydrogen phosphide. 
PH30 (missing). 
PH302 hypophosphorous acid. 
PH^O^ phosphorous acid. 
PH^O* phosphoric acid. 

Phosphoric acid is formed from phosphorus oxychloride 
(phosphoryl trichloride) by the action of water. 

(POyCP + 3H^0 = (POy''(OH)^ + 3HC1 



HYPOPHOSPHOROUS ACID. 181 

The same product is obtained when water acts upon phos- 
phorus pentachloride, POP. It may be assumed that the five 
chlorine atoms are replaced by hydroxyl groups, and the re- 
sulting (unknown) compound, P(OH)^, is, by the loss of a 
molecule of water, converted into phosphoric acid. 
P(0H)5 = H^O + (P0)(0H)3 

Phosphorous acid results from the action of water on phos- 
phorus trichloride, and might, therefore, be supposed to be 
derived from the latter by the replacement of the three chlo- 
rine atoms by three hydroxyl groups. Its chemical properties 
indicate, however, that in it the phosphorus plays the part of a 
pentatomic element : it is phosphoryl, (PO)'", combined with 
one hydrogen atom and two hydroxyl groups. 

InhypophosphorOus acid it must be admitted that phosphoryl 
is united to two atoms of hydrogen and one hydroxyl group. 

The constitution of the three acids is expressed by the 
formulae 



roH 


(H 


(H 


\"' \ OH 


PO''' \ OH 


PO'''-^ H 


(oh 


(OH 


(oh 


isphoric acid. 


Phosphorous acid. 


Hypophosphorous acid. 



HYPOPHOSPHOEOUS ACID. 

H3P02 

When phosphorus is boiled with milk of lime or with a con- 
centrated solution of baryta, a soluble hypophosphite is pro- 
duced, and on treating the solution of barium hypophosphite 
with sulphuric acid, a precipitate of barium sulphate and a 
solution of hypophosphorous acid are obtained ; they may be 
separated by filtration. When sufficiently concentrated, the 
liquor leaves a colorless and syrupy residue, which, when cooled 
to 0°, deposits white crystals of the acid. 

This acid is decomposed at a high temperature, yielding 
phosphoric acid and hydrogen phosphide. It is gifted with 
energetic reducing properties : it instantly decomposes the salts 
of mercury and silver, setting free the metal. An excess of 
hypophosphorous acid added to a solution of cupric sulphate 
precipitates, by the aid of a gentle heat, hydride of copper, 
Cu^H^, which is decomposed at 100° into copper and hydrogen 
(A. Wurtz). 

16 



182 ELEMENTS OF MODERN CHEMISTRY. 

Hypopliospliorous acid contains three atoms of hydrogen, 
only one of which is capable of being replaced by an equiva- 
lent quantity of a metal. The composition of the hypophos- 
phites is consequently expressed by the following general 
formula : 

in which Bf represents a monatomic metal, such as potassium, 
capable of replacing hydrogen atom for atom. 

PHOSPHOROUS ACID. 

H3P03 

Preparation. — Phosphorous acid results from the action of 
water upon phosphorus trichloride, as already seen. It may 
be obtained in a state of purity by evaporating the acid liquor 
resulting from this reaction, and heating the syrupy residue 
in a platinum capsule until the odor of hydrogen phosphide 
is perceptible. On cooling, the acid solidifies to a crystalline 
mass. 

Properties. — These crystals absorb moisture when exposed 
to the air, and are resolved into an intensely acid liquid ; they 
melt at a gentle heat, and are decomposed by a high tempera- 
ture into hydrogen phosphide and phosphoric acid. 

Like hypophosphorous acid, phosphorous acid possesses re- 
ducing properties. 

Its boiling aqueous solution reduces the salts of mercury, 
silver, and gold, and this reduction is favored by the presence 
of ammonia. It converts arsenic acid into arsenious acid. 

Chlorine, bromine, and iodine convert it into phosphoric acid 
in presence of water. 

ffPO' H- H^O + CP = 2HC1 + HTO* 

Phosphorous acid contains three atoms of hydrogen, two of 
which are replaceable by an equivalent quantity of a metal. 
It is hence called a dibasic acid. 

The composition of the neutral phosphites is expressed by 
the general formula 

R'2HP0^ 

in which B! represents a monatomic metal like potassium or 
sodium. 



PHOSPHORIC OXIDE — PHOSPHORIC ACID. 183 



PHOSPHOKIC OXIDE, OR PHOSPHOEUS 
PENTOXIDE. 

(PHOSPHORIC ANHYDRIDE.) 
P205 

This compound may be obtained by burning phosphorus in 
a large globe filled with dry air. A dense white smoke is pro- 
duced, and condenses upon the walls of the vessel in flakes like 
snow. This body is the anhydride of phosphoric acid. When 
exposed to the air, it absorbs moisture and is converted into 
metaphosphoric acid. 

FO^ + H^O = 2HP0^ 

When thrown into water it dissolves with a hissing noise, 
such as is produced by a red-hot iron. 

Phosphoric oxide volatilizes at a dull-red heat ; it is unde- 
composable by heat. It yields the oxychloride when distilled 
with phosphorus pentachloride. 

p205 + 3PCP = 5P0CP 

Phosphorus pentoxide is much used in the laboratory for 
drying gases, and as a dehydrating agent. 

PHOSPHORIC ACID. 

(ORTHOPHOSPHORIC ACID.) 

H3P0* 

Preparation. — 1. This acid may be prepared by boiling 
phosphorus with nitric acid. On account of the violence of 
the reaction the operation is difficult to regulate, and even 
dangerous when ordinary phosphorus is employed, but it 
succeeds very well with powdered amorphous phosphorus. 
This is heated with tolerably concentrated nitric acid in a 
retort, fitted with a receiver, and, when the whole of the phos- 
phorus has disappeared, a little nitric acid is added to the 
contents of the retort, and the liquid is concentrated in a 
platinum capsule. When the last portions of nitric acid have 
been driven out, a small quantity of water is added, and the 
syrupy liquid is placed in a bell-jar over a dish containing 
concentrated sulphuric acid. At the end of some time, the 



184 ELEMENTS OP MODERN CHEMISTRY. 

phosplioric acid is deposited in the form of hard, transparent, 
prismatic crystals. 

2. A current of chlorine may be passed through warm water 
under which is a layer of melted phosphorus. Phosphoric 
acid and hydrochloric acid are formed. 

PCP + 4:W0 ^ WFO' + 5HC1 

As soon as all of the phosphorus has disappeared the solution 
is evaporated, and the hydrochloric acid is driven out by 
heating the residue to 200°. The residue is dissolved in water 
and forms a solution which will deposit the acid in crystals 
when concentrated as indicated above. 

Properties. — When exposed to the air, these crystals attract 
moisture and deliquesce. Their solution is very acid. It does 
not coagulate white of egg, and it produces no cloud in a solu- 
tion of barium chloride, but it forms a white precipitate of 
ammonio-magnesium phosphate in a solution of magnesium 
sulphate on the addition of ammonia. With silver nitrate to 
which ammonia has been added, it gives a yellow precipitate 
of trisilver phosphate, Ag^PO*. Orthophosphoric acid contains 
three atoms of hydrogen, each of which is replaceable by an 
equivalent quantity of metal. 

PYROPHOSPHORIC ACID. 

When orthophosphoric acid is heated for a long time to 
213° it loses water and is converted into a new acid, which is 
called pyrophosphoric. Two molecules of phosphoric acid lose 
one molecule of water, and then unite to form a single mole- 
cule of pyrophosphoric acid. 

/OH 
PO^OH /OH 

PO^OH XqH 

^OH 

The residue constitutes an opaque, semi-crystalline mass, 
composed almost entirely of pyrophosphoric acid. 



METAPHOSPHORIC ACID. 185 

Its aqueous solution forms a white precipitate of silver 
pyrophosphate in solutions of silver nitrate. 

H^P^O^ + 4AgN0^ = Ag^P^O^ 4- 4HN0' 

When heated with water, pyrophosphoric acid again com- 
bines with one molecule of that liquid, and is converted into 
phosphoric acid by a reaction the inverse of that by which it 
is formed. 

METAPHOSPHORIC ACID. 

HP03 

Preparation. — When phosphoric acid is heated to redness 
in a platinum crucible, a hard, transparent, vitreous mass is 
obtained on cooling ; this is metaphosphoric acid. 

It is formed by the abstraction of one molecule of water 
from phosphoric acid. 

HTO* — H^O = HPO^ 

It may also be obtained directly from calcium acid phos- 
phate, the preparation of which from bone-ash has already been 
described. A slight excess of dilute sulphuric acid is added 
to the concentrated solution of this salt, and the insoluble cal- 
cium sulphate formed is separated by filtration. Since, how- 
ever, the calcium sulphate is not entirely insoluble in water, 
the solution is concentrated, and alcohol added, which com- 
pletely precipitates the sulphate. The liquid is again filtered, 
the alcohol driven off by evaporation, and the residue heated 
to a temperature near redness to remove the excess of sulphuric 
acid. 

On cooling, a vitreous mass of metaphosphoric acid is ob- 
tained. 

An aqueous solution of metaphosphoric acid instantly pro- 
duces a precipitate of silver metaphosphate in a solution of 
silver nitrate. 

HPO^ + AgNO^ = AgPO^ + HNO' 

A few drops of the acid solution added to white of egg sus- 
pended in water produces an abundant white precipitate. 

The same metaphosphoric acid is formed when phosphoric 
oxide is thrown into a large quantity of cold water, or when it 
is allowed to deliquesce in the air. Under these circumstances, 

16* 



186 ELEMENTS OF MODERN CHEMISTRY. 

one molecule of phosphoric oxide combines with only one 
molecule of water. 



The preceding considerations establish the existence of three 
phosphoric acids, which differ both in composition and proper- 
ties. To these three acids correspond three salts of silver, and 
it will be seen that the latter differ from the acids only by 
containing silver instead of hydrogen, a substitution which 
takes place atom for atom. 

ACIDS. SILVER SALTS. 

H^PO* phosphoric acid (orthophos- Ag^PO* trisilver phosphate (ortho- 

phorie). phosphate). 

jj4p207 pyrophosphoric acid. Ag^P^O^ silver pyrophosphate. 

HPQS metaphosphoric acid, AgPO^ silver metaphosphate. 

It may be added that, independently of the acids and salts 
of which the composition and nomenclature have just been 
considered, others have been described, the most interesting 
of which are related to the metaphosphates, of which they con- 
stitute polymeric modifications. That is, two, three, four, or 
more molecules of metaphosphoric acid are condensed in a 
single molecule, forming more complicated acids. 

COMPOUNDS OF PHOSPHOEUS AND SULPHUR. 

When phosphorus is heated with dry sulphur, or when a 
mixture of the two bodies is melted under water, they combine 
with a vivid combustion which is sometimes accompanied by 
dangerous explosions. The action is less violent with amor- 
phous phosphorus. According to the proportions of these 
bodies which are brought into contact, several combinations of 
phosphorus and sulphur may be obtained, among which the 
trisulphide, P^S^, and the pentasulphide, P^S^, correspond to 
phosphorous and phosphoric oxides. The pentasulphide may 
be obtained in pale yellow crystals. 



ARSENIC. 

Vapor density conipared to air 10.37 

Vapor density compared to hydrogen .... 150. 
Atomic weight As = 74.45 

Arsenic was discovered by A. Schroeder in 1694. 

Natural State and Extraction. — There exists in nature ^ 



ARSENIC. 187 

common and abundant mineral which contains iron, snlphur, 
and arsenic, and whicli is called mispichel ; it is a sulphar- 
senide of iron. When it is strongly heated, the arsenic is 
volatilized and a residue of iron sulphide remains. 

FeSAs = FeS + A^ 

Mispickel. Iron sulphide. 

The operation is conducted on the large scale in earthenware 
cylinders placed horizontally in a furnace. The arsenic sublimes 
into sheet-iron pipes fitted to the open extremity of the cylin- 
ders which extend beyond the furnace. The volatilization of 
the arsenic is facilitated by the addition of a certain quantity 
of metallic iron. 

The arsenic of commerce may be purified by distilling it with 
charcoal in a stoneware retort. 

Properties. — Recently-sublimed arsenic presents the appear- 
ance of a steel-gray, crystalline mass, having a metallic lustre. 
Its crystalline form is an acute rhombohedron. Its density is 
about 5.7. 

Arsenic volatilizes without melting at a temperature below 
dull redness. Its vapor is yellow. When it is heated under 
strong pressure it melts to a transparent liquid. On exposure 
to the air it loses its lustre and assumes a black-gray color ; in 
this case its surface becomes covered with a thin layer of a 
brown-black pulverulent substance, regarded by some chemists 
as a suboxide of arsenic. 

Arsenic oxidizes when it is 
heated in the air or in oxygen. 

If a small quantity of arsenic 
be thrown upon a red-hot coal, 
white vapors are produced, and 
an alliaceous odor is percep- 
tible. 

A fragment of arsenic may 
be strongly heated in the hori- 
zontal branch of a tube con- 
taining oxygen (Fig. 71) ; the 
metal takes fire and burns with ^^^' ' • 

bluish flame, producing white vapors of arsenious oxide. 

If arsenic be preserved from the air under a layer of water, 
in which it is insoluble, it oxidizes slowly, in such a manner as 
to form a small quantity of arsenious acid, which dissolves in 




188 ELEMENTS OP MODERN CHEMISTRY. 

the water. This property explains the efficacy of powdered 
arsenic (commercial cobalt) for poisoning flies. 

Powdered arsenic sprinkled into dry chlorine burns with 
bright scintillations into the trichloride AsCP. Arsenic also 
combines directly with bromine, with iodine, and with sulphur. 

Arsenic is used to alloy the lead used for the manufacture 
of shot, which are thereby rendered more spherical in form, 
and so hardened that they will not foul the gun. 

HOROGEN ARSENIDE (ARSINE). 

Density compared to hydix)gen 39 

Molecular weight AsH^ =78 

Preparation. — This gas may be prepared by the action of 
hydrochloric acid upon zinc arsenide. 

Zn^As^ + 6HC1 = 2.K%W + 3ZnCP 

Zinc arsenide. Zinc chloride. 

It must be handled with prudence, as it is extremely poisonous. 

Properties. — Hydrogen arsenide is colorless; its odor is 
penetrating and garlicky. At a red heat it is decomposed 
into arsenic and hydrogen. On the application of flame, it 
burns in the air with a bluish light, producing fumes of 
arsenious oxide. If the supply of air be insufficient, arsenic 
is deposited. With one and a half times its volume of oxygen, 
hydrogen arsenide forms an explosive mixture, the products of 
the combination being water and arsenious oxide. 
4AsH3 + 60^ := As*0« + GH^O 

Chlorine decomposes hydrogen arsenide with a flash of light 
and formation of hydrochloric acid. An excess of chlorine 
yields arsenic trichloride, but in the presence of water, arsenious 
oxide is formed. 

4AsH^ -j- 12CP + eH^O = As*0^ + 24HC1 

Water dissolves about one-fifth of its volume of hydrogen 
arsenide. When this gas is agitated with a solution of cupric 
sulphate, it disappears entirely if the gas be pure, and leaves 
a residue of hydrogen should that gas have been present in 
the free state in the mixture (Dumas). 

3CuS0* -f 2AsH3 = Cu^As^ -f- SH^SO* 

Cupric sulphate. Copper arsenide. 

Silver nitrate solution decomposes hydrogen arsenide ; silver 
is precipitated, and arsenious acid formed. 
AsH^ -f 6AgN0^ 4-3H^O = H^AsO^ + 6HN0' + 6Ag 






ARSENIC CHLORIDE — ARSENIOUS OXIDE. 189 

ARSENIC CHLORIDE. 

AsCP 

Preparation. — 1. When dry chlorine is passed over pow- 
dered arsenic, arsenic chloride distils and condenses as a yellow 
liquid, containing an excess of chlorine, from which it may be 
freed by distillation over arsenic (Dumas). 

2. A mixture of arsenious oxide and sulphuric acid is gently 
heated in a retort, and fragments of fused sodium chloride gradu- 
ally added ; arsenic chloride distils and condenses in the receiver. 
6H^S0^ + 12NaCl + As'^O^ = 6Na^S0* + 4 AsCP + 6H^0 

Sodium chloride. Sodium sulphate. 

Properties. — Arsenic chloride is a colorless, oily, and very 
dense liquid. It boils at 134°. Its density at 0° is 2.205. It 
gives off white fumes in the air, and is very poisonous. 

An excess of water instantly decomposes it into hydrochloric 
acid and arsenious oxide, which, being but slightly soluble, is 
precipitated. 

4AsCP + 6W0 = As^O« + 12HC1 

Arsenic bromide and iodide are formed in an analogous 
manner. A fluoride, AsF', is also known, and may be pre- 
pared by distilling a mixture of arsenious oxide, fluor spar, and 
sulphuric acid in a lead retort. It is a colorless liquid. 

ARSENIOUS OXIDE. 

As*06 

Preparation. — This dangerous poison is obtained in the 
arts by roasting arseniferous minerals, particularly mispickel. 
Roasting is an operation which consists in heating a mineral 
in contact with air, by which the oxidizable elements present 
are oxidized. When arseniferous minerals are roasted, arsen- 
ious oxide is formed among other products, and volatilizes, and 
is condensed either in wide horizontal chimneys or in a large 
building divided into numerous communicating compartments, 
through which the vapor is led consecutively. It is collected 
in the form of a powder, and is resublimed in cast-iron pots 
surmounted by sheet-iron cylinders, in which it condenses. 

Properties. — Recently-sublimed arsenious oxide occurs as 
vitreous masses ; but it soon loses its transparency and becomes 
milk-white, presenting the appearance of porcelain. When a 
large piece of the opaque oxide is broken, the interior is usually 
found to be still transparent and vitreous. 



190 ELEMENTS OF MODERN CHEMISTRY. 

Arsenious oxide then exists in two forms : the vitreous 
variety is amorphous ; the opaque is crystalline. The former 
variety changes into the latter by a molecular transformation 
which takes place in the midst of the amorphous vitreous mass. 

Arsenious oxide crystallizes in regular octahedra or in tetra- 
hedra ; sometimes, but more rarely, in right-rhombic prisms. 
It is dimorphous. 

It dissolves slowly in cold water, in which it is but slightly 
soluble, and in this respect there is a curious difference between 
the opaque and the vitreous varieties. The latter is three times 
more soluble than the former ; while one part of the vitreous 
oxide dissolves in 108 parts of water at 15°, one part of the 
opaque variety requires 355 parts of water for its solution at 
the same temperature. 

The aqueous solution of arsenious oxide feebly reddens blue 
litmus. It is almost tasteless. It may be regarded as contain- 
ing normal arsenious acid, H^AsO^, corresponding to normal 
phosphorous acid, H^PO^ ; but this hydrate cannot be separated 
from the solution. On evaporation, the oxide As*0^ is always 
deposited. 

4H^AsO^ = As^O« + 6W0 

The aqueous solution of arsenious oxide, neutralized with 
ammonia, gives a green precipitate with solution of cupric sul- 
phate ; this is copper arsenite, or Scheele's green. With silver 
nitrate it gives a canary-yellow precipitate of silver arsenite. 

Arsenious oxide is more soluble in hydrochloric acid than in 
water. If a slip of clean copper be introduced into this solu- 
tion, it becomes covered with a steel-gray or black coating of 
arsenic. 

Reinsch's test for arsenic consists in boiling the suspected 
substance with dilute hydrochloric acid and bright metallic 
copper. The arsenic is deposited upon the copper, and by 
carefully heating the latter in a small tube the arsenic vola- 
tilizes and is converted into arsenious oxide, which condenses 
in the crystalline form, easily recognizable by aid of a micro- 
scope. 

By the action of zinc the solution of As*0® in hydrochloric 
acid disengages hydrogen arsenide ; the zinc displaces the hy- 
drogen of the hydrochloric acid, and, by the action of this 
nascent hydrogen upon the arsenious oxide, water and hydro- 
gen arsenide are formed. 

AsW -f 12H2 = 6R'0 -f lAsH' 



ARSENIOUS OXIDE. 



191 



Marsh's Apparatus. — The reducing action of nascent hy- 
drogen upon arsenious oxide is used for the detection of ihis 
substance by the aid of JlarsJis apparatus. 

This consists of an apparatus for the generation of hydrogen 
(Fig. 72) ; it contains pure zinc and dilute sulphuric acid, and the 
hydrogen burns at the 
drawn-out jet with an 
almost colorless flame. 
If, however, a few 
drops of a solution of 
arsenious oxide be in- 
troduced by the fun- 
nel-tube, the character 
of the flame is at once 
changed ; it becomes 
bluish, elongated, and 
diff"uses a white smoke, 
and if a white porce- 
lain surface be de- 
pressed into it, large 
spots of a brownish 
color are produced. 
These are composed 
of arsenic, which is set free in the interior of the flame by 
the decomposition of the hydrogen arsenide by the heat. 




Fig. 72. 




Fig. 73 represents a more perfect form of Marsh's appa- 
ratus. The hydrogen, mixed with the hydrogen arsenide^ first 



192 ELEMENTS OP MODERN CHEMISTRY. 

traverses a tube filled with cotton, to arrest small drops of liquid 
which are carried with the gas ; it then passes through a hard 
glass tube constricted at several points and heated near one of 
the constrictions. The hydrogen arsenide is decomposed and 
the arsenic deposited in the narrow and cooled portion of the 
tube. Lasfly, the gas is passed through a solution of silver 
nitrate, which retains as arsenious acid any arsenic that might 
escape as undecomposed hydrogen arsenide (see page 188). 

Marsh's apparatus permits the detection of the least trace 
of arsenious or arsenic acid in a liquid. It is of great value 
in medico-legal researches in cases of suspected poisoning by 
arsenic. 

ARSENIC ACID 
H^AsO* 

Preparation. — When arsenious oxide is heated with nitric 
acid having a specific gravity of 1.35, red vapors are disen- 
gaged and the oxide is oxidized into arsenic acid, which may 
be obtained as a syrupy liquid by sufficient concentration. 
When left for a long time in a cool place it deposits colorless 
crystals, which constitute a hydrate 2H^AsO* 4- H^O (E. 
Kopp). These crystals are very deliquescent, and dissolve in 
water with the production of cold. They melt at 100°, losing 
their water of crystallization, and there remains a mass com- 
posed of fine needles of the normal acid H^AsO*. 

When heated for some time to a temperature between 140 
and 180°, this acid loses water, and is converted into fyro- 
arsenic acid^ H*As^O^ 

2H^AsO* — H^O = WMO' 

Between 200 and 206° another quantity of water is driven 
out, and on cooling there remains a pasty, pearly mass, which 
is metarsenic acid, HAsO^. 

ff AsO* — H^O = HAsO^ 

It will be noticed that in their modes of formation and in 
their constitution, arsenic, pyro-arsenic and metarsenic acids are 
analogous to the corresponding acids of phosphorus. 

When metarsenic acid is heated to dull redness, it loses all 
of its hydrogen in the form of water, and is converted into 
arsenic oxide, As^O^. 

2HAsO^ — H^O = As^O^ 



COMPOUNDS OF SULPHUR AND ARSENIC. 193 

At this temperature the oxide melts, and at a bright-red 
heat it is decomposed into arsenious oxide and oxygen. 

2As20^ = As*0« + 20^ 

When exposed to the air it absorbs moisture, but very slowly, 
and even when treated with water it requires a certain time for 
solution. 

Ordinary arsenic acid, which may be called ortharsenic, is 
very soluble in water ; its solution strongly reddens blue litmus 
and possesses a very acid taste. It is reduced by nascent hydro- 
gen, like the solution of arsenious oxide. When neutralized 
with ammonia, it forms a bluish-white precipitate with solution 
of cupric sulphate, and a red-brown precipitate with silver 
nitrate. Hydrogen sulphide produces no immediate precipitate. 

A solution of sulphurous acid reduces arsenic acid to arse- 
nious oxide, and then on the addition of hydrogen sulphide, a 
yellow precipitate of arsenic sulphide, As^S^ is formed. 

COMPOUNDS OF SULPHUR AND ARSENIC. 

Three sulphides of arsenic are known: 

Arsenic disulphide, or realgar As^S^ 

Arsenic trisulphide, or orpiment As^S^ 

Arsenic pentasulphide As^S^ 

Arsenic Bisulphide, As^Sl — This body occurs in nature in 
the form of transparent red crystals, which belong to the type 
of the oblique rhombic prism. 

It is obtained as a red mass having a conchoidal fracture by 
melting 75 parts of arsenic with 32 parts of sulphur. It is 
fusible, and may be crystallized by slow cooling. When strongly 
heated in closed vessels, it boils and distils without alteration, 
but when heated in the air, it burns into arsenious and sulphur- 
ous oxides. The alkaline sulphides and ammonium sulphide 
dissolve realgar, leaving a brown powder which has been con- 
sidered as a subsulphide of arsenic. Boiling solution of potas- 
sium hydrate also dissolves realgar, forming a mixture of 
potassium arsenite and sulpharsenite ; the latter is a soluble 
compound of arsenic trisulphide and potassium sulphide; a 
brown powder remains undissolved. 

Arsenic Trisulphide, or Orpiment, As^S^ — When a solu- 
tion of arsenious oxide is submitted to the action of hydrogen 
in 17 ^ 



194 ELEMENTS OF MODERN CHEMISTRY. 

sulphide, the liquid assumes a yellow color without the forma- 
tion of any precipitate, but if a drop of hydrochloric acid be 
added, a yellow, flocculent precipitate of arsenic trisulphide is 
formed at once. 

AsW + 6H^S = 2As^S^ + GH'^O 

The composition of arsenic trisulphide corresponds to that 
of arsenious oxide, and is the same as that of the orpiment 
found in nature. 

It may also be obtained by fusing together arsenic and sul- 
phur in the proper proportions, or even arsenious oxide and 
sulphur; in the latter case, sulphurous oxide is disengaged, 
and arsenic trisulphide sublimes. Thus prepared, orpiment 
occurs as crystalline masses of a yellow color, bordering upon 
orange, and a pearly aspect. Its density is 3.459. It is fusible 
and volatile. 

Arsenic trisulphide obtained by precipitation is insoluble in 
cold water, and but slightly soluble in boiling water, but it is 
very soluble in ammonia. By continued boiling with water, it 
yields hydrogen sulphide and arsenious acid (de Clermont 
and Frommel). It is also dissolved by solutions of the alka- 
line sulphides with the formation of sulpharsenites, compounds 
of two sulphides, in which the alkaline sulphide plays the part 
of a base and the arsenic trisulphide the part of an acid 
Orpiment also dissolves in solutions of the caustic alkalies with 
the formation of an arsenite and a sulpharsenite. 

Arsenic PentasulpMde, As^S^ — When an excess of hydro- 
gen sulphide is passed into solution of arsenic acid heated to 
70°, arsenic pentasulphide is precipitated (Bunsen). Also 
when 9, sulpharsenate of an alkali is decomposed by a mineral 
acid. 

2Na3AsS* + 3H=^S0* = SNa^SO* + As^S^ + 3H^S 

It is a lemon-yellow powder, may be fused and distilled with- 
out alteration, and is insoluble in water. 

The alkaline sulphides dissolve it with the formation of 
sulpharsenates. Among the latter there is one having the 
composition K^AsS*, and which corresponds to the arsenate 
K^AsO*. It is formed by the following reaction : 

As^S^ + SK^S = 2(K3AsS0 



ANTIMONY. 195 

ANTIMONY. 

Sb = 119.5 

Antimony is generally classed with tlie metals. It indeed 
possesses the lustre of a metal, and it conducts heat and elec- 
tricity; but in a true chemical classification these physical 
properties cannot overbalance the most striking chemical anal- 
ogies. By its affinities, and by the nature and constitution of 
its compounds, antimony must find a place by the side of 
arsenic, which must itself be classed with phosphorus and 
nitrogen. 

Metallurgy of Antimony. — The most common ore of anti- 
mony is stibmte, Sb^S^, and was known to the ancients. The 
metal is extracted from it by a very simple process. The sul- 
phide is first separated by fusion from the earthy materials, 
called gangue, with which it is associated ; it is then roasted 
or heated in contact with air. The sulphur is in great part 
expelled in the form of sulphurous oxide gas, and the antimony 
is converted into oxide, which still contains some undecom- 
posed sulphide. The whole is then pulverized, and the pow- 
der mixed with pulverized charcoal impregnated with sodium 
hydrate. This mixture is calcined in crucibles, and the anti- 
mony oxide and a portion of the sulphide are reduced by the 
charcoal ; sodium sulphide is also formed, and this dissolves a 
portion of the antimony sulphide, forming a flux which floats 
upon the molten antimony ; after cooling, the latter is found 
at the bottom of the crucible as a button, easy to separate from 
the scoriae. 

By another process the antimony sulphide is fused with 
metallic iron. Iron sulphide and antimony are formed, and 
the latter collects at the bottom by reason of its greater 
density. 

Perfectly pure antimony is prepared in the laboratory by 
reducing antimonous or antimonic oxide by charcoal. 

Properties. — Antimony is a brilliant white metal, having a 
slightly bluish lustre ; it is brittle, and has a laminated frac- 
ture. Its density is 6.715. It melts at about 630°, and 
sensibly vaporizes at a white heat. 

Antimony may be crystallized by allowing large masses of 
the fused metal to cool slowly, and decanting the liquid por- 
tion. Small acute rhombohedra may be obtained in thigi 
manner. 



196 ELEMENTS OF MODERN CHEMISTRY. 

When heated in contact with air, antimony is converted into 
antimonous oxide, Sb*0^ If the flame of a blow-pipe be 
directed upon a fragment of antimony in a cavity scraped in 
a piece of charcoal, the metal melts, becomes red-hot, and gives 
off white fumes. If now the molten globule be allowed to fall 
to the floor, it breaks up into a multitude of smaller globules, 
and each particle rebounds as a brilliant spark, leaving behind 
it a train of smoke. 

Powdered antimony burns brilliantly in dry chlorine. 

Type metal contains 20 per cent, antimony and 80 per cent, 
lead ; the alloy is hard, and takes a sharp impression of the 
mould. Other useful alloys of antimony are Britannia metal 
and various antifriction metals. 

HYDROGEN ANTIMONIDE (STIBINE). 

There is a compound of hydrogen and antimony which cannot 
be obtained in the pure state at ordinary temperatures, but which 
is the body SbH'. It is decomposed by heat, and the decom- 
position of the pure compound begins between — 65 and — 56° ; 
it can be prepared largely diluted with hydrogen by the action 
of nascent hydrogen upon a solution containing antimony : when 
decomposed by heat it forms metallic rings and mirrors^ which 
it is of importance to distinguish from those formed by arsenic. 
The following differences are sufficient for this purpose : 

The antimony rings are not displaced when heated in a 
current of hydrogen ; the arsenic rings are volatilized, and 
condense in a cooler portion of the tube. 

The spots and rings of antimony are not dissolved by a solu- 
tion of sodium hypochlorite (Labarraque's solution), which at 
once dissolves those of arsenic. 

The antimony spots are readily dissolved by a drop of nitric 
acid, and the liquid leaves on evaporation a white residue, 
which is not colored by the addition of a drop of silver nitrate 
solution. Under the same circumstances, the arsenical spots 
leave a white residue, which assumes a brick-red color when 
moistened with a solution of silver nitrate, owing to the for- 
mation of silver arsenate. 

COMPOUNDS OF ANTIMONY AND CHLORINE. 

Antimony trichloride SbCP 

Antimony pentachloride SbCl^ 

Antimony Trichloride, SbCP. — This compound; formerly 



COMPOUNDS OF OXYGEN AND ANTIMONY. 197 

known as butter of antimony, is formed by the action of by- 
drocbloric acid upon antimony sulpbide. It is generally pre- 
pared in tbe laboratory from the residue from the preparation 
of hydrogen sulphide. This acid liquid is distilled in a retort 
provided with a receiver, which is changed as soon as the anti- 
mony chloride which distils over begins to crystallize in the 
neck of the retort. 

This chloride is solid, transparent, and colorless. It melts 
at 73.2°, and boils at 230°. It dissolves in water charged 
with hydrochloric acid, forming a colorless solution, but when 
this liquid is diluted with water there is formed an abundant 
white precipitate, long known as powder of Algaroth. It is 
an oxychloride of which the composition does not appear con- 
stant. There is one which contains SbOCl, and which can be 
regarded as antimony trichloride, in which two atoms of chlo- 
rine have been replaced by one atom of oxygen. 

Antimony Pentachloride, SbCP. — This is formed by the 
action of an excess of chlorine upon antimony or upon the 
trichloride. It is a yellow liquid, giving off white fumes in the 
air. It is volatile, but cannot be distilled without undergoing 
a partial decomposition into chlorine and antimony trichloride. 
When exposed to the air, it absorbs moisture and is converted 
into a crystalline mass, which is a hydrate of the pentachloride. 
When treated with a large excess of water, it is decomposed 
with production of heat, and formation of pyrantimonic and 
hydrochloric acids. 

An antimonous bromide, SbBr^, and an iodide, SbP, are 
known, and the fluorides, SbF^ and SbF^, have also been 
obtained. 



COMPOUNDS OF OXYGEN AND ANTIMONY. 

Two oxides of antimony are known, corresponding to those 
of phosphorus and arsenic : 

Antimonous oxide SMO^ 

Antimonic oxide Sb^O^ 

Normal antimonic acid, H^SbO*, corresponding to phosphoric 
and arsenic acids, is not known in the free state, but a derivative 
of this acid exists and may be regarded as antimony antimonate. 
Its composition is Sb^O*, and it is derived from antimonic acid 

17* 



198 ELEMENTS OF MODERN CHEMtSTRY. 

by the substitution of an atom of antimony for three atoms of 
hydrogen. 

H^SbO* antimonic acid. 
SbSbO* antimony antimonate. 

There is a pyrantimonic and also a metantimonic a<;id, 
analogous to the corresponding phosphorus acids : 

H^Sb^C pyrantimonic acid. 
HSbO^ metantimonic acid. 

ANTIMONOUS OXIDE. 

Sb^oe 

This is obtained by oxidizing the metal in the air. The 
operation may be conducted in two crucibles placed one above 
the other, an opening being pierced in the upper one for the 
access of air. They are heated to redness in a furnace, and on 
cooling, the antimony is found to be partially converted into 
brilliant needles formerly known as silver flowers of anti- 
mony. The crystals are right rhombic prisms, mixed with 
regular octahedra, for antimonous oxide crystallizes in two 
forms, presenting the same character of dimorphism as arsenious 
oxide. The two compounds are hence said to be isodimorphous. 

When solution of sodium hydrate, or better, sodium carbon- 
ate, is poured into solution of antimony trichloride, a white 
precipitate of antimonous hydrate is formed, and, in the latter 
case, carbonic acid gas is disengaged. 

SbCP + SNaOH =. W^W + SNaCl 

Sodium hydrate. Antimonous hydrate. Sodium chloride. 

This hydrate readily parts with a molecule of water, being 
converted into another hydrate, HSbOl 

H^SbO^ — H^O = HSbO^ 
ANTIMONY ANTIMONATE. 

This compound is formed when antimonous oxide is heated 
for a long time in the air, oxygen being absorbed, or when 
antimonic oxide is strongly calcined, oxygen being then disen- 
gaged. 

It is a white, infusible powder, undecomposable by heat and 
insoluble in water. 



ANTIMONIC OXIDE AND ACIDS. 199 



ANTIMONIC OXIDE AND ACIDS. 

When powdered antimony is heated with concentrated nitric 
acid, a white powder is obtained, which is metantimonic acid. 
It contains one atom of hydrogen capable of being replaced by 
an equivalent quantity of metal, and thus corresponds to meta- 
phosphoric acid. 

HPO^ HSbO^ KSbO^ 

Metaphosphoric acid. Metantimonic acid. Potassium metantimonate. 

When it is heated to dull redness, it loses water and is con- 
verted into antimonic oxide. 

2HSbO^ — H^O = Sb^O^ 

If antimony pentachloride be poured into an excess of 
water, a white precipitate of pyrantimonic acid is formed. 
It is the analogue of pyrophosphoric acid, and, like the latter, 
contains four atoms of hydrogen. 

H*FO^ H^Sb^O^ K^Sb^O^ 

Pyrophosphoric acid. Pyrantimonic acid. Potassium pyrantimonate. 

According to Fremy, potassium pyrantimonate may be 
obtained by heating metantimonic acid or potassium metanti- 
monate with potassium hydroxide, in a silver crucible. 

+ ffO 



2KSbO^ + 


2K0H 


= K^Sb^O^ 


Potassium 


Potassium 


Potassium 


metantimonate. 


hydrate. 


pyrantimonate. 



The metantimonate may be extracted by water, in which 
it is soluble, from the white mass, formerly designated dia- 
phoretic antimony^ which is obtained by deflagrating in a red- 
hot crucible a mixture of 2 parts of nitre (potassium nitrate) 
and 1 part of powdered antimony. Cold water first dissolves 
potassium nitrate from this mass, and then potassium metanti- 
monate. The solution of the latter salt produces with hydro- 
chloric acid a white precipitate of metantimonic acid. 

SULPHIDES OF ANTIMONY. 

Two sulphides of antimony are known : 

Antimony trisulphide, or antimonous sulphide . . Sb^S' 
Antimony pentasulphide, or antimonic sulphide . . Sb^S^ 

Antimonous Sulphide, Sb^S^. — This compound, ordinarily 
galled sulphide of antimony, occurs both in the crystalline 



200 ELEMENTS OF MODERN CHEMISTRY. 

form and amorplious. Crystallized, it exists in nature and is 
the mineral commonly known as stihnite. It is separated from 
its gangue by fusion, and is thus obtained in gray masses com- 
posed of brilliant needles having a metallic lustre. 

Amorphous, it constitutes the orange-colored precipitate 
formed by the action of hydrogen sulphide upon a solution of 
antimony chloride. The precipitate is insoluble in ammonia, but 
dissolves in ammonium sulphide and in the alkaline sulphides. 

Antimony trisulphide is reduced by hydrogen at a high tem- 
perature ; hydrogen sulphide is formed, and antimony remains. 

When heated in the air, antimony sulphide is oxidized with 
formation of sulphur dioxide and antimonous oxide. The 
incompletely roasted residue melts at a red heat, and on cool- 
ing assumes the form of a brown vitreous mass called glass 
of antimony. It is an impure oxysulphide which appears to 

contain the compound Sb^S'^O = ^i ^ > 0. 

Antimony trisulphide is used in pyrotechny, adding to the 
brilliancy of colored fires. 

Antimony Pentasnlphide, Sb^S^, is obtained as an orange- 
red powder by passing hydrogen sulphide through a solution 
of the pentachloride in hydrochloric acid. It is more generally 
prepared as follows : Finely-pulverized antimony trisulphide is 
digested with sulphur and a solution of sodium hydrate, or a 
mixture of sulphur, sodium carbonate, and lime ; the antimony 
sulphide gradually dissolves in the liquid, and the product of 
the reaction is a sulphantimonate of sodium, which is deposited 
in fine crystals from the concentrated liquid. 

Sb^S^ + 3Na=^S = 2Na3SbS* 

Sodium sulphide. Sodium sulphantimonate. 

It is soluble in water, and on the addition of hydrochloric 
acid to its solution, hydrogen sulphide is disengaged and anti- 
mony pentasnlphide is precipitated. 

2Na^^SbS* + 6HC1 = 6NaCl + Sb'S^ -f 3H^S 



General Considerations upon the Elements of the Nitro- 
gen Group. — Nitrogen, phosphorus, arsenic, and antimony, 
and bismuth might be added, form a group of elements allied 
by the most striking analogies. This is made manifest by the 
atomic composition of their compounds, as will be seen in the 
following synopsis : 



BORON. 



201 



HYDROGEN COMPOUNDS. 




Ammonia. Hydrogen phosphide. Hydrogen arsenide. 


SbH^ 

Hydrogen antimonide. 


CHLORINE COMPOUNDS. 




NOP PCP AsCP 

Nitrogen Phosphorus Arsenic 
trichloride. trichloride. trichloride. 


SbCP 

Antimony 
trichloride. 



— PCP — SbCP 

Phosphorus pentachloride. Antimony pentachloride. 

OXYGEN COMPOUNDS. 

N*0^(?) V'O' As-'O^ SbW 

Nitrogen trioxide. Phosphorous oxide. Arsenious oxide. Antimonous oxide. 

N^O^ FO^ As^O^ Sb^O^ 

Nitrogen pentoxide. Phosphoric oxide. Arsenic oxide. Antimonic oxide. 



_ 


H3P03 


H^AsO^ 


H^SbO^ 




Phosphorous acid. 


Arsenious acid. 


Antimonous acid. 


HNO^ 


___ 





HSbO^ 


Nitrous acid. 






Antimonyl hydrate. 





HTO* 


H^AsO* 







Phosphoric acid. 


Arsenic acid. 







HT^O' 


H*As^O^ 


msb^o^ 




Pyrophosphoric acid. 


Pyro-arsenic acid. 


Pyro-antimonic acid. 


HNO^ 


HPO^ 


HAsO^ 


HSbO^ 


Nitric acid. 


Metaphosphoric acid. 


Metarsenic acid. 


Metantimonic add. 



If tbe analogy between nitrogen and phosphorus were com- 
plete, there should be an orthonitric acid, H^NO* = HNO^ + 
H^O, corresponding to ordinary or orthophosphoric acid. This 
acid is not known as a definite hydrate, but compounds exist 
which are derived from it. Thus, bismuth subnitrate, BiNO*, 
can be regarded as a salt of orthonitric acid, in which three 
atoms of hydrogen are replaced by one atom of triatomic 
bismuth. 



BORON. 

B -^ 10.9 

Boron is found in boric acid and in borates. Among the 
more important of the latter are sodium borate or borax, 
calcium borates or horocalcite and colemanite, and calcium 
sodium borate, known as horonatrocalcite. The elemeot was 



202 ELEMENTS OF MODERN CHEMISTRY. 

first isolated by Gay-Lussac and Thenard in 1808, by fusing 
boric oxide with potassium. It occurs in several modifications. 
Preparation. — Amorphous boron is obtained by reducing 
boric oxide with sodium in an iron crucible. 

23^0^ 4- Na^ == SNaBO^ + B 

Boric oxide. Sodium metaborate. 

A more convenient method consists in heating an intimate 
mixture of 100 parts anhydrous borax with 50 parts magne- 
sium powder to redness in a well-covered crucible. The pow- 
dered mass is thoroughly washed, first with water then with 
hydrochloric acid, and dried at 100°. 

Adamantine boron is prepared by fusing boric oxide with 
an excess of aluminium. The boron set free is dissolved by 
the aluminium, and on slow cooling separates in crystals, whose 
color varies from yellow to dark brown, according to the nature 
of the impurities, aluminium and carbon, one or both of which 
they invariably contain. These crystals may be isolated by 
treating the cold mass with hydrochloric acid. 

Properties. — Amorphous boron is infusible, but may be 
volatilized by the intense heat of the electric furnace. When 
heated to 300° in the air, it burns into boric oxide. Its com- 
bustion in pure oxygen is very brilliant, and it possesses a 
singular affinity for nitrogen, with which it combines directly 
at a red heat, forming a nitride, BN. In an atmosphere of 
nitric oxide, it burns into a mixture of boric oxide and boron 
nitride (Wohler and Deville). 

Boron decomposes water at a red heat, and otherwise behaves 
as an energetic reducing agent. 

Adamantine boron crystallizes in quadratic octahedra, having 
a density of 2.6, and a hardness and brilliancy next to diamond. 
It is infusible, and strongly resists the action of oxidizing 
agents and alkaline solutions. Hampe and Joly consider the 
crystals to be definite compounds of boron with aluminium and 
carbon. 

BORON CHLORIDE. 
BCP 

Preparation. — This body may be prepared by heating crude 
amorphous boron in a current of chlorine, or by the action of 
chlorine on an incandescent mixture of boric oxide and charcoal. 

B^O^ + 3C + 3CP = 2BCP + SCO 

Boric oxide. Boron chloride. Carbon monoxide, 



BORON FLUORIDE. — BORIC ACID. 203 

Properties. — In a state of purity, boron chloride is a color- 
less, mobile, and highly-refractive liquid, boiling at 17°. It 
fames in the air, and is readily decomposed by water into boric 
and hydrochloric acids. 

BCP + 3H^0 = 3HC1 + B(0H)3 

BORON FLUORIDE. 
BF3 

Density compared to air 2.31 

Density compared to hydrogen 34. 

Preparation. — Boron flucn^ide was discovered by Gay-Lussac 
and Thenard in 1810. It is prepared by heating in a glass 
retort an intimate mixture of one part of boric oxide and two 
parts of powdered calcium fluoride with twelve parts of sul- 
phuric acid. The gas disengaged is collected over mercury. 

3CaF2 + B^O^ -f 3WS0' = 3CaS0^ + 3W0 -f 2BF^ 

Calcitim Boric oxide. Calciiun sulphate, 

iluoride. 

Properties. — Boron fluoride is a colorless gas, having a suf- 
focating odor. It produces abundant fumes in the air, and is 
very soluble in water, which dissolves about 800 times its 
volume of this gas. Its affinity for water is so great that it 
carbonizes paper and analogous organic substances, from which 
it removes the elements of water. 

The solution of boron fluoride in water is accompanied by a 
chemical reaction ; when the aqueous solution of this gas, satu- 
rated at the ordinary temperature, is cooled to 0°, crystals of 
boric acid are deposited, and a very acid liquid is obtained, 
known as hydrofluoboric acid ; its composition is expressed by 
the formula : 

BF^H = BFIHF 

BORIC ACID. 
H3B03 

Preparation. — Boric acid was discovered by Homberg in 
1702. It is found in the ft^ee state in the craters of certain 
volcanoes, and exists in solution in the lagoni of Monte- 
Rotondo, in Tuscany. These are muddy little lakes, through 
which arise the gaseous emanations from the fissures of a vol- 
canic soil. The gases {suffioni) contain sensible traces of boric 



204 ELEMENTS OF MODERN CHEMISTRY. 

acid, which is dissolved by the water of the lagoni. On evap- 
oration, this water furnishes the crude boric acid. 

Large quantities of boric acid are also obtained from the 
native borates of sodium, calcium, and magnesium, which 
are decomposed by dissolving them in hot hydrochloric acid. 
The boric acid then separates upon cooling. 

In the laboratory, boric acid is prepared by decomposing a 
boiling saturated solution of borax or sodium borate with dilute 
sulphuric acid. The latter is added in small portions until 
the liquid strongly reddens litmus-paper ; the solution is then 
allowed to cool, and the boric acid separates in the crystalline 
form. 

Properties. — Pure boric acid crystallizes in pearly scales, 
somewhat greasy to the touch. It dissolves in 25 parts of 
water at 18°, and is much more soluble in boiling water. The 
solution is feebly acid, and changes blue litmus solution to a 
wine color. Boric acid dissolves in alcohol, and the solution 
burns with a green flame. 

When heated to 100° it loses one molecule of water, and is 
converted into metahoric acid, HBOl If the latter be main- 
tained for a time at a temperature of 140°, it is converted into 
tetraboric acid, H'B*0^ 

4HB02 = H"B*0' + H^O 

When boric acid is heated in a platinum crucible to a tem- 
perature near redness, it loses all of its water, melts, and solidi- 
fies to a transparent glass on cooling. This is boric oxide. 

2H^B0^ = B'^0^ -f 3ffO 

At a red heat this body dissolves a great number of solid sub- 
stances, particularly the metallic oxides ; it then yields variously 
colored glasses on cooling. 

Boric oxide is not decomposed by charcoal at a red heat, but 
is converted into boron chloride by the simultaneous action of 
chlorine and charcoal. 



SILICON. 

Si = 28.2 
Like boron, silicon exists amorphous and in the crystalline 
form. It was discovered by Berzelius in 1825. 

Preparation. 1. Amorphous >S'it7zco?i,— Dry sodium silico- 



SILICON. 205 

fluoride is heated with half its weight of metallic sodium : 
sodium fluoride is formed and silicon is set free. 

Na=^FlSiF* + 2Na2 = 6NaF + Si 

Sodium silico-fluoride. Sodium fluoride. 

On cooling, the mass is exhausted, first with cold, and then 
with hot, water ; a brown powder of amorphous silicon remains. 

Impure silicon is readily prepared by heating to redness a 
mixture of fine quartz sand and magnesium powder in a test-tube. 
SiO' + 2Mg = 2MgO + Si 

2. Crystallized Silicon. — Deville and Caron obtained crys- 
tallized silicon by projecting a mixture of 3 parts of potassium 
and silicon double fluoride, 4 parts of zinc, and 1 part of 
sodium into a red-hot crucible. Fluoride of sodium is formed, 
and the silicon set free dissolves in the zinc and separates in 
the crystalline form on cooling; it is isolated from the zinc 
by dissolving the button in hydrochloric acid; the silicon 
remains in the form of brilliant laminae or needles. Crystal- 
lized silicon is most conveniently prepared by reducing the 
oxide SiO^ by charcoal in the electric furnace (Moissan). 

Properties. — Amorphous silicon is a brown powder, more 
dense than water, in which it is insoluble, and producing dark 
stains on the fingers. When heated in the air, it takes fire and 
burns with a bright light into silicic oxide, SiO^. 

Crystallized silicon has a density of 2.49. It may be heated 
to redness in oxygen without taking fire, but when it is calcined 
with potassium carbonate the latter is decomposed with a vivid 
emission of light, potassium silicate being formed and carbon 
being set free. Crystallized silicon resists the oxidizing action 
of both potassium nitrate and potassium chlorate, but it dis- 
solves slowly in a boiling solution of potassium hydrate, hydro- 
gen being disengaged and potassium silicate being formed. It 
burns when heated to redness in an atmosphere of chlorine, 
and takes fire spontaneously in fluorine. 

HYDEOaEN SILICIDE. 

Probable formula SiH^ 

Preparation. — This compound was discovered by Wohler 
and Bufi'in 1857. Magnesium silicide"^ is introduced into a 

* This is most readily prepared by heating one part finely pulverized 
quartz sand with one and a half parts magnesium powder. 

18 



206 ELEMENTS OF MODERN CHEMISTRY, 

two-necked bottle, which is then entirely filled with water that 
has been recently boiled. To one of the necks of the bottle is 
fitted a funnel-tube which passes to the bottom of the bottle ; 
to the other, a delivery-tube leading to the pneumatic trough ; 
this tube also is completely filled with water so that there is 
no air in the whole apparatus. Concentrated hydrochloric acid 
is then introduced by the funnel-tube, and immediately reacts 
with the magnesium silicide, forming magnesium chloride, 
which dissolves, and gaseous hydrogen silicide, which must 
be collected in jars filled with recently boiled water. 

Properties. — The gas thus obtained is not pure hydrogen 
silicide ; it contains an excess of hydrogen. It is colorless and 
insoluble in water : water containing air in solution oxidizes it. 

If bubbles of the gas be allowed to escape through the water 
of the trough, each bubble takes fire on coming to the surface, 
producing a bright light and a smoke of silicic oxide, which forms 
rings like those produced by hydrogen phosphide under similar 
circumstances, but often colored brown by a portion of silicon 

SILICON CHLORIDE. 

SiCl* 

This compound is formed when silicon is heated to dull red- 
ness in a current of chlorine, or when the latter gas is passed 
over an incandescent mixture of charcoal and silica. 

SiO^ -f C^ + CI* = SiCl* -f 2C0 

Preparation. — Precipitated silica, lamp-black, and oil are 
intimately mixed into a stiff" paste. This paste is made into 
little balls, which are put into a crucible, the cover of which is 
then luted on, and the whole is heated to redness in a furnace. 
When cool, the balls are introduced into a porcelain tube or a 
clay retort (Fig. 74), which is then heated to bright redness, 
while a current of carefully-dried chlorine is passed through. 
The silicon chloride and the carbon monoxide formed are 
passed through two U tubes surrounded by a mixture of ice 
and salt. The silicon chloride is thus condensed. 

An easier method of preparation consists in gently heating 
in a current of chlorine the crude product obtained by reducing 
silica with magnesium. Silicon chloride distils, and is condensed 
in a freezing mixture (Gattermann). 

Properties. — Silicon chloride is a volatile, colorless liquid, 
of an irritating odor. It fumes in the air. Its density is 1.52, 
and it boils at 59°. 



SILICON TLUORIDE. 



207 



It is instantly decomposed by water, silicic and hydrochloric 
acids being formed. A part of the silicic acid is precipitated 




Fig. 74. 

in the form of a jelly, while another part remains in solution. 
The latter is perhaps a hydrate corresponding to the chloride. 
SiCl* + 4ffO = 4HC1 -f Si(OH)* 

There exist a tetrabromide of silicon, SiBr*, and a tetraiodide, 
SiP, both corresponding to the chloride just described. 

Besides these compounds there are also known the tri-halides, 
Si^CP, Si^Br«, and Si^P, as well as silicon chloroform, SiHCP, 
and the analogous compounds of bromine and iodine. 

SILICOI^ FLUOBIDE. 

SiF* 
Density compared to air 3.6 

Density compared to hydrogen 52. 

Preparation. — An intimate mixture of silicious sand and 
finely-powdered calcium fluoride, or fluor spar, is introduced 
mto a glass flask (Fig. 75), and a sufficient quantity of sul- 
phuric acid is added to reduce the whole to a creamy consistence. 
A gentle heat is applied, and the gas disengaged may be col- 
lected over mercury. 



208 



ELEMENTS OF MODERN CHEMISTRY. 




2CaF^ -f 2H2SO* -f SiO^ = 2CaS0* + SiF* + 2H20 

Calcium fluoride. Silicic oxide. Calcium sulphate. 

Properties. — S i 1 i c o n 
fluoride is a, colorless, suf- 
focating gas, producing 
white fumes when allow- 
ed to escape into the air. 
It may be liquefied by a 
low temperature and a 
strong pressure. On con- 
tact with water it is de- 
composed, silicic hydrate 
separating in gelatinous 
flakes, and hydrofluosili- 
cic acid being formed. 

3SiF* + 4H20 
=z 2(H2F2.SiF*) + H2Si03 
r IG. 75. Hydrofluosilicic acid. 

Hydrofluosilicic Acid. — A saturated, aqueous solution of 
this acid is a highly acid liquid, fuming in the air, and evapor- 
ating slowly at 40° from a platinum-dish, leaving no residue. 

It is prepared by passing gaseous silicon fluoride into water 
under which is a layer of mercury. The delivery-tube must 
dip beneath the surface of the mercury, so that the silicon flu- 
oride can only come in contact with the water after passing 
through the metal ; otherwise the delivery- tube would become 
obstructed by the deposit of gelatinous silica. 

Hydrofluosilicic acid is employed as a reagent in the labora- 
tory. It precipitates the salts of potassium and sodium, form- 
ing insoluble fluosilicates, R^FlSiF*. 

SILICA. 

Si02 

Native State. — Silicic oxide is widely diffused in nature. 
It occurs crystallized in the various quartzes, and as tridymite ; 
cryptocrystalline, as agate, chalcedony, carnelian, flint, etc. ; 
granulated, it is found in sandstones and the sand produced by 
their disaggregation ; in this case it is often mixed with variable 
quantities of alumina and oxide of iron. 

Rock-crystal is pure silicic oxide. It occurs as six-sided 
prisms, terminated by pyramids of six faces (Fig. 76). 

Amorphous silica exists in various minerals, such as qpaZ 
and hydropTiane, It is also found in the form of pulverulent 



SILICA. 



209 




Fig. 76. 



deposits and in solution in many running waters, in large 
proportion in the liot waters of the geysers in Iceland. 

Properties. — Quartz is colorless when pure ; its density is 
2.69, and it is No. 7 in the scale of hardness (page 789). 
It is very refractory : in the oxyhydrogen 
flame it undergoes a viscous fusion, but 
can be melted to a clear liquid, and even 
volatilized, by means of the electric fur- 
nace (page 210). It forms a bluish vapor. 
It is not attacked by acids, with the excep- 
tion of hydrofluoric acid. Boiling alkaline 
solutions scarcely afi"ect it, but the amor- 
phous varieties of silica, such as flint, as 
well as opal and the other hydrates, dis- 
solve more readily in boiling solutions of 
the alkaline hydroxides. 

All of the varieties of silica, when heated 
to redness with the alkalies or alkaline car- 
bonates, combine with the bases, forming 
silicates which enter into fusion at a high temperature and 
solidify to a vitreous mass on cooling. Potassium silicate, 
or soluble glass^ is a transparent mass, soluble in water. When 
hydrochloric acid is added to this solution, potassium chloride 
is formed and silicic acid is precipitated as a gelatinous mass, 
which is not insoluble in water. An aqueous solution of silicic 
acid may be obtained. 

If hydrochloric acid be added to a dilute solution of potas- 
sium silicate, the liquid remains transparent although it contains 
silicic acid. It may be poured into a dialyser, composed of a 
piece of parchment-paper stretched over a wooden or glass ring, 
and floated on the surface of pure water contained in another 
vessel. The potassium chloride gradually passes through the 
membrane, as would any crystallizable body, and the silicic 
acid remains alone dissolved in the water in the dialyser, as 
all other amorphous bodies which are soluble in water would 
do. Graham gave the name dialysis to this separation of crys-, 
tallizable bodies, which he named crystalloids^ from uncrystal- 
lizable bodies, which he named colloids^ by means of certain 
membranes. The former bodies pass through the membranes, 
which are, however, impermeable to the colloids. 

The silicic acid which remains in solution probably consti- 
tutes normal or ortho-silicic acid, Si(OH)*. By the loss of a 
o 18* 



210 



ELEMENTS OF MODERN CHEMISTRY. 



molecule of water, this tetrabasic acid would be converted into 
dibasic metasilicic acid, SiO(OH)l Many of the natural sili- 
cates represent salts of these acids: olivine^ Mg^SiO*, and 
garnet^ APCa^(SiO*)^, are orthosilicates, while Wollasfomte, 
CaSiO^, and enstatite, MgSiO^ are metasilicates. A numerous 
class of minerals correspond to more complex acids resulting 
from the condensation of two or more molecules of ortho- and 
meta-silicic acids. Felspar, for example, has the composition 
AlKSi^O^, and must be regarded as a salt of the polysilicic 
acid, H^Si^O^. 

Grlass is a mixture of potassium or sodium silicate with cal- 
cium silicate, and generally contains aluminium silicate. It is 
made by the prolonged fusion of potassium or sodium carbon- 
ate with pure quartz sand and lime. Flint glass contains lead, 
introduced in the form of red lead. Colored glasses are ob- 
tained by adding metallic oxides to the above ingredients. 
Cuprous oxide gives red glass; cupric oxide, green; cobalt 
oxide, blue, etc. Soda glass is more fusible than potash glass. 

The Electric Furnace. — The highest temperatures which 
were formerly employed in chemical operations were those 
produced by the oxyhydrogen blow-pipe. This has been 




Fig. 77. 



recently supplanted by a device known as the electric fur- 
nace, in which the energy of powerful electric currents is 
converted into heat. The temperatures which can be thus 
reached and maintained far exceed 3000°. Nearly all those 
bodies which were formerly regarded infusible and non-vola- 
tile have been melted and vaporized in the electric furnace, 
and many new products have been obtained by its means. 



CARBON. 211 

A simple forai of electric farnace, constructed hj Moissan, is 
shown in Tig. 77. It consists of a block of lime, cut in two, hol- 
lowed out at the centre, and perforated to permit the introduction 
of the carbon electrodes. The arc formed between these plays upon 
the substance in the cavity, and is regulated by moving the carbons ; 
its position is controlled by a powerful magnet. 



CARBON. 

C = 11.97 

Natural State and Varieties. — The carbon of chemists is 

pure charcoal. This substance is known to all ; black, friable, 
light, absolutely fixed, inalterable by the air at ordinary tem- 
peratures, but combustible when heated in the air, it results 
from the calcination of organic matters, and particularly wood, 
in closed vessels. But carbon by no means always reveals 
these same properties. It occurs in nature under forms so 
different that it is impossible to apply a general description to 
all of its known varieties. What could be more different, as 
far as physical properties are concerned, from the soot deposited 
by a smoky flame, or the light, porous, and opaque charcoal, 
than the hard, dense, and transparent substance found in nature 
iu the form of diamond ? Nevertheless, these bodies are com- 
posed of one and the same substance, carbon ; alike, they all 
burn in oxygen at a high temperature, producing carbon 
dioxide. 

Among the various forms which carbon assumes, and which 
constitute one of the most curious examples of dimorphism, 
the following may be described : 

Diamond. — This is the hardest of all bodies ; it scratches all 
others, and can only be trimmed by grinding with its own dust. 

It is found crystallized in the form of the 
regular octahedron and various fornas de- 
rived fi'om it, such as the rhombic dodeca- 
hedron, trisoctahedron, and hexoctahe- 
dron. The faces are generally convexly 
curved (Fig. 78). 

Moissan has succeeded in obtaining the 
diamond artificially. He dissolved carbon 
in molten iron, the temperature being raised yiq. 78. 

to 3000°. Upon chilling the mass, a portion 
of the carbon crystallized out, and though exceedingly small, 
the crystals showed all the characteristics of the diamond. 




212 ELEMENTS OF MODERN CHEMISTRY. 

The density of the diamond is between 3.50 and 3.55. It is 
a bad conductor of heat and electricity ; it strongly refracts and 
disperses light. From this latter fact Newton first divined its 
combustible nature, which was proved, in 1694, by the Floren- 
tine academicians of del Cimento^ who burned a diamond in the 
focus of a concave mirror. Lavoisier and Davy repeated this 
celebrated experiment, and proved that the sole product of the 
combustion is carbon dioxide. At the temperature of the 
electric arc the diamond swells up and blackens, being con- 
verted into graphite. 

Graphite, or Plumbago. — This is a crystalline variety of 
carbon, which is found in primitive rocks in brilliant steel-gray 
foliated masses. It sometimes occurs in hexagonal laminse. 
It can be scratched with the finger-nail, and leaves a black 
trace when drawn over paper. Its density is 2.2, and it con- 
ducts heat and electricity. It burns only at very high tem- 
peratures; ordinarily, it contains from one to two per cent, of 
foreign matters. 

It has been obtained artificially. Molten iron possesses the 
property of dissolving carbon at a very high temperature, and 
depositing it on solidifying in hexagonal scales of graphite. 

Graphite is converted into a yellow substance known as 
graphitic acid when treated with a mixture of nitric acid 
and potassium chlorate. The diamond is not attacked by 
this mixture. 

Plumbago is used for the manufacture of lead-pencils and 
crucibles, and as a lubricant, and is sometimes called black lead. 

There are other natural substances popularly regarded as 
varieties of carbon, but they are very impure. Their carbon is 
combined with more or less hydrogen, and they are in fact 
mixtures of complex hydrocarbons. They are : 

Anthracite^ a hard and compact variety of carbon containing 
from 8 to 10 per cent, of earthy matters. 

Bituminous coal, a brilliant, black variety, strongly impreg- 
nated with bituminous and earthy matters. It has been pro- 
duced by the slow decomposition of vegetable matters buried 
in the earth in the early geological ages. This origin is indi- 
cated by the impressions of leaves, stems, and fruits, which are 
evident in certain specimens of this coal. It contains only 
from 75 to 88 per cent, of carbon. When it is calcined in 
closed vessels, it disengages combustible gases and products 
which may be condensed in the liquid form and then separate 
into two layers. One is aqueous and ammoniacal, while the 



CARBON. 



213 



other is composed of tar. The residue of the distillation of 
bituminous coal is coUe. The interior walls of the cast-iron 
vessels in which coal is distilled become covered with a coni- 
pact layer of a gray, dense, hard and sonorous carbon, which 
is a good conductor of heat and electricity. This is the carbon 
of gas-retorts, and is produced by the igneous decomposition 
of hydrocarbons rich in carbon, which are disengaged during 
the calcination of the coal. 

Fat coals are those which burn with a long flame, softening 
in burning ; dry coals burn with a short flame which produces 
less heat than the preceding. 

Lignite is a combustible mineral containing less carbon, and 
more impure than bituminous coal ; it is found in the lower, 
tertiary formations. Natural jety which is employed for the 
manufacture of ornaments, is a variety of lignite. 

Among the artificial carbons, independently of coke, may be 
mentioned wood charcoal, lamp-black, and animal charcoal. 

Wood Charcoal. — When wood is calcined in closed vessels 
it leaves a residue which is ordinary charcoal. It is prepared 
on the large scale by two processes, carbonization in stacks, 
which is carried on in the forests, and distillation in closed 
vessels. Charcoal is amorphous, brittle, and sonorous, a bad 
conductor of heat and electricity. Its density does not ex- 
ceed 1.57. The lighter varie- ^^ 
ties are the more combustible. 
Its combustion leaves a resi- ( 
due of one or two per cent, of 
ash, formed principally of min- \ 
eral salts, among which the 
most abundant are the car- 
bonates of calcium and potas- 
sium. 

Lamp-hlack is produced by 
the incomplete combustion of 
organic substances rich in car- 
bon. When rosin or tallow is 
burned, a dense smoke is pro- 
duced which is composed of 
particles of carbon that have 
escaped combustion. In the 
arts, lamp-black is procured by burning rosin in cast-iron pots, 
C (Fig. 79), heated by a fire, F. The vapors given off" are ig- 
nitedj and the smoke is conducted into a chamber, A, the walls 




Fig. 79. 



214 ELEMENTS OP MODERN CHEMISTRY. 

of which are hung with canvas. On this the lamp-black is de- 
posited, and is detached by lowering the cone B, which acts as 
a scraper. Lamp-black is not pure carbon. It contains tarry 
and oily matters, from which it may be freed by calcination in 
a covered crucible. It is used for the manufacture of printing- 
inks. 

Animal charcoal is produced by calcining animal matters, 
such as blood, the debris of skin, horn, bone, etc., in closed 
vessels. Bone-black or ivory-black contains the calcareous 
salts, calcium phosphate and carbonate, which form the base 
of the osseous tissue. The carbon is consequently disseminated 
through a porous mass. These salts may be extracted by 
treating the bone-black with dilute hydrochloric acid, by which 
they are dissolved. The residue, washed with water and dried, 
is known as washed or purified animal charcoal. 

Absorbent Properties of Charcoal. — The amorphous and 
porous varieties of carbon, of which several forms have been 
described, possess the property of absorbing and retaining in 
their pores, gases, liquid and solid bodies. It is to this absorp- 
tive faculty that are due the decolorizing and disinfecting 
properties of charcoal, which are made use of to a large extent 
in the arts. 

If a piece of incandescent charcoal be plunged into mercury 
that it may cool out of contact with the air, and then be intro- 
duced into a small jar filled with ammonia or hydrochloric acid 
over the mercury-trough, the gas is at once absorbed and the 
mercury rises in the jar. 

The following table, by Th. de Saussure, indicates the quan- 
tities of several gases which are absorbed by one volume of 
charcoal : 

1 volume of charcoal absorbs 90 volumes of ammonia. 





u 


85 


a 


hydrochloric acid. 




« 


65 


ii 


sulphur dioxide. 




<( 


65 


(( 


hydrogen sulphide 




{< 


40 


(( 


nitrous oxide. 




tt 


35 


ft 


carbon dioxide. 




tt 


9.42 


<( 


carbon monoxide. 




tt 


9.25 


f( 


oxygen. 


tt 


tt 


7.50 


(( 


nitrogen. 


<( 


tt 


1.75 


« 


hydrogen. 



I 



Charcoal increases in weight when exposed to the air, for 
it absorbs and condenses the atmospheric moisture. When 
plunged into water charged with a small quantity of hydrogen 
sulphide, it absorbs that gas and removes the odor of the water. 



CAEBON. 



215 



The disinfecting properties of charcoal are thus easily explained. 
It is well known that charcoal will remove the unpleasant odor 
of corrupted waters, of meats slightly spoiled, and in general 
of organic matters in a state of putrefaction. A layer of char- 
coal between two layers of sand is an excellent filter for the 
clarification of drinking waters. 

The decolorizing properties of charcoal are another mani- 
festation of this general faculty of absorption, which is pos- 
sessed in the highest degree by animal charcoal. If litmus 
solution or red wine be agitated with a sufficient quantity of 
animal charcoal and subsequently filtered, the liquids pass 
through colorless. 

This property of animal charcoal is largely applied in the 
arts, particularly for decolorizing sugars and syrups. 

Chemical Properties - Carbon is distinguished by its pow- 
erful affinity for oxygen, 
an affinity which is not, 
however, exercised ex- 
cept at high tempera- 
tures. It only combines 
with oxygen at a red 
heat, and remains incan- 
descent as long as com- 
bination goes on, the 
heat produced by the 
combination being suffi- 
cient to maintain the 
incandescence. In pure 
oxygen it burns with 
a brilliant light. The 
product of the combus- 
tion is carbonic acid gas. 

By the aid of heat, ^' 
carbon decomposes a 
great number of oxy- 
genized compounds, re- 
moving and combining with the whole or a part of their oxygen. 
This decomposition takes place at comparatively low tempera- 
tures when the oxygenized body does not strongly retain its 
oxygen ; in this case, carbon dioxide is formed, and the reduc- 
tion of cupric oxide by charcoal furnishes an example. In the 
contrary case, the reduction, that is, the decomposition of the 




216 ELEMENTS OF MODERN CHEMISTRY. 

oxidized body, requires a very high temperature ; carbon mo- 
noxide is then formed. The reduction of zinc oxide by charcoal 
is an example. 

If an incandescent charcoal be rapidly plunged under a bell- 
jar filled with water on the pneumatic trough, bubbles of gas 
arise and collect in the jar (Fig. 80). They are formed of a 
mixture of hydrogen, carbon monoxide, and a small quantity 
of carbon dioxide. These gases are produced by the decom- 
position of the water by the charcoal, which was red-hot at the 
moment of contact with the liquid. 

C -f H=^0 = H^ + CO carbon monoxide. 

Water gas, a mixture of hydrogen and carbon monoxide, is 
made, according to this reaction, by passing steam over highly- 
heated coal, coke, or other form of carbon. 

Carbon combines directly with sulphur at a high tempera- 
ture, forming carbon disulphide. 

Carborundum, CSi. — At the high temperature of the elec- 
tric furnace and under the influence of the current, carbon 
reduces silica; the product of the reaction is a transparent green- 
ish or yellowish mass of crystals having a hardness but little 
below that of the diamond, and used as a substitute for diamond 
for cutting and polishing under the name carborundum. It is 
unaffected by acids, even by hydrofluoric acid, but is decom- 
posed by fusion with alkalies. This substance is a definite 
compound of carbon and silicon, as indicated by the formula. 

Carbides of Boron. — Boric oxide, like silica, is reduced by car- 
bon in the electric furnace, the boron combining with the excess of 
carbon to form carbides of definite composition. One of these, B^C^, 
resembles graphite, but is fusible at very high temperatures. Another 
carbide, CB^, is said to be harder even than the diamond (Moissan). 

COMPOUNDS OF CARBON AND OXYGEN. 

Two compounds of carbon and oxygen are known : 

Carbon monoxide CO 

Carbon dioxide, or carbonic acid gas CO^ 

The latter body, which has long been known as carbonic 
acid, is the oxide corresponding to the true carbonic acid, 
which would be 

CO^ + ff = WGO' 

This normal carbonic acid is as yet unknown : it is doubtless 
too unstable to exist in the free state. However, its existence 



CARBON MONOXIDE. 



217 



may be admitted, for a corresponding compound is known in 
sulphocarbonic acid H^CS^. 



CARBON MONOXIDE. 

Density compared to air 0.967 

Density compared to hydrogen 13.9 

Molecular weight CO = 27.78 

Preparation. — 1. An intimate mixture of zinc oxide and 
charcoal may be calcined in a clay retort. 

ZnO 4- C = CO + Zn 
2. A convenient method of preparing carbon monoxide con- 
sists in beating oxalic acid with an excess of sulphuric acid in 
a glass flask. The oxalic acid loses the elements of water, 
which it yields to the sulphuric acid, and breaks up into carbon 
dioxide and carbon monoxide. 

en^O* r= CO 4- co^ + H^O 

Oxalic acid. Carbon monoxide. „arbon dioxide. 




The mixture of the two gases is passed through a wash-bottle, 
B (Fig. 81), containing a solution of potassium hydroxide, by 

K 19 



218 ELEMENTS OF MODERN CHEMISTRY. 

which the carbon dioxide is absorbed, potassium carbonate being 
formed. The carbon monoxide may then be collected over water. 
Another excellent method consists in heating a mixture of 
one part of powdered potassium ferrocyanide with ten parts 
of concentrated sulphuric acid. The carbon monoxide evolved 
is practically pure. 

K*Fe(CN)6 + 6H2SO* + GH^O = 2K2SOHFeSO* + 3(NH*)2SO* + 6C0 

Potassium Ferrous 

ferrocyanide. sulphate. 

Properties. — Carbon monoxide is a colorless, odorless gas. 
Its critical conditions are — 139.5° and 35.5 atmospheres ; the 
liquid boils at — 190° and freezes at — 207°. Carbon monox- 
ide is neutral, and does not cloud lime-water, which distin- 
guishes it from carbon dioxide. It extinguishes burning bodies, 
but is combustible itself, burning in the air with a blue flame, 
and forming carbon dioxide. It is not only unfit for respira- 
tion, but is very poisonous, combining with and profoundly 
altering the red corpuscles of the blood. 

Composition. — If two volumes of carbon monoxide be 
mixed with one volume of oxygen in an eudiometer, and a 
spark be passed, complete combustion takes place, and the 
three volumes of the mixture are reduced to two volumes 
of carbon dioxide. This can be verified by passing into the 
eudiometer a solution of potassium hydrate, which will com- 
pletely absorb the new gas. 

It hence follows that two volumes of carbon monoxide con- 
tain the same quantity of carbon as two volumes of carbon 
dioxide. Knowing from other circumstances that two volumes 
of carbon dioxide contain two volumes of oxygen, it follows 
that two volumes of carbon monoxide contain one volume of 
oxygen. Its molecular formula is therefore CO. 

Carbon monoxide undergoes dissociation at a very high 
temperature, and may be resolved into carbon and oxygen. 

It is almost insoluble in water, but is absorbed by a solution 
of cuprous chloride in hydrochloric acid (Doyere and F. Le 
Blanc). Advantage is taken of this property in volumetric 
analysis to separate carbon monoxide from certain other gases. 

When heated for a long time to 100°, in sealed tubes with 
potassium hydroxide, it combines with the alkali, forming potas- 
sium formate (Berthelot). 

CO + KOH = KCHO^ 

Potassium hydroxide. Potassium formj^te, 



CARBON DIOXIDE. 219 

Action of Chlorine upon Carbon Monoxide. — Under the 
influence of sunlight, carbon monoxide combines directly with 
an equal volume of chlorine, forming a gas which is known as 
carhonyl chloride, or phosgene. The volume of the carbonyl 
chloride is one-half that of the sum of the combining gases, 
so that its formula is COCP. 

Carbonyl chloride may be easily condensed to a colorless 
liquid, boiling at 8.2°. Its vapor is colorless, produces a suffo- 
cating sensation, and provokes tears. It is instantly decomposed 
by water, with the formation of carbon dioxide and hydro- 
chloric acid. 

COCP + H^O = 2HC1 + CO^ 

Its mode of formation, its composition, and its properties 
indicate its relations to carbon dioxide. 

2 volumes CO absorb 2 volumes of chlorine to form 2 volumes CO.Cl* 
2 volumes CO absorb 1 volume of oxygen to form 2 volumes CO.O 

Carbon monoxide thus plays the part of a radical ; it com- 
bines directly with oxygen or with chlorine to form either 
oxide or chloride of carbonyl. 

L. Mond has discovered a remarkable class of compounds 
of carbon monoxide with certain metals. Nickel carhonyl^ 
Ni(CO)*, may be considered as the type of these compounds ; 
it is formed by passing carbon monoxide over finely divided 
nickel at a temperature of 100°. It condenses at low tempera- 
tures to a colorless, highly refracting liquid having a density 
of 1.35, and boiling at 43°. At a temperature below 200°, it 
decomposes into carbon monoxide and metallic nickel. 



CARBON DIOXIDE. 

Density compared to air 1.524 

Density compared to hydrogen 21.83 

Molecular weight CO^ . = 42.73 

This gas was discovered by Black in 1757, and its composi- 
tion was recognized by Lavoisier in 1776. It is one of the 
constituents of the atmosphere, and is the product of a great 
number of reactions which take place on the earth's surface, 
such as the combustion of carbon and organic matters, respira- 
tion, and the phenomena of putrefaction and fermentation. It 
issues from the soil of volcanic countries. 



220 ELEMENTS OF MODERN CliEMISTRy. 

Preparation. — Fragments of marble, which is calcium car- 
bonate, are introduced into a two-necked bottle fitted with a 
delivery-tube and a safety -tube (compare Fig. 11, page 60). 
The bottle is half-filled with water, and hydrochloric acid is 
gradually added by the funnel-tube. An effervescence im- 
mediately takes place, due to the disengagement of carbon 
dioxide. 

CaCO^ + 2HC1 = CO^ + CaCP -f H^O 

Calcium carbonate. Calcium chloride. 

The gas is most conveniently collected by dry downward 
displacement, like chlorine. 

When it is desired to prepare large quantities of the gas, 
a self-regulating generator, such as that described on page 
102, is advantageously used. Acid vapors and other impuri- 
ties are removed by passing the gas through a saturated solu- 
tion of potassium acid carbonate. 

Yery pure carbon dioxide is also obtained by heating the 
acid carbonates of the alkaline metals. 

2NaHC0^ r= CO^ + Na^CO^ + H^O 

Sodium acid carbonate. Sodium carbonate. 

On a large scale, the gas is manufactured by heating lime- 
stone or magnesite. 

Composition. — 1. If carbon be burned in oxygen, the latter 
is converted into carbon dioxide without changing its volume. 
Hence two volumes of carbon dioxide contain two volumes of 
oxygen. These two volumes of oxygen, which represent two 
atoms, are combined with one atom of carbon, and the compo- 
sition of a molecule of carbon dioxide is hence expressed by 
the formula 

CO^ = 2 volumes. 

2. Dumas and Stas determined the centesimal composition 
of carbon dioxide by burning a known weight of diamond in 
oxygen, and carefully weighing the carbon dioxide produced. 
By subtracting the weight of the diamond burned from that of 
the carbon dioxide, the weight of the oxygen was determined. 
The apparatus employed is represented in Fig. 82. 

The increase in weight of the tubes L, M, N, 0, P indicates 
the quantity of carbon dioxide formed. 

Dumas and Stas thus found that 100 parts of carbon dioxide 
contain 

Carbon 27.27 

Oxygen r . . 72.73 

100.00 



CARBON DIOXIDE. 



221 




222 



ELEMENTS OF MODERN CHEMISTRY. 



a centesimal relation which corresponds to the proportion of 
one atom of carbon to two atoms of oxygen : 

Carbon 11.97 

Oxygen 31.76 

Physical Properties. — Carbon dioxide is colorless ; it has a 
feeble, somewhat pungent odor. A litre of this gas at 0°, and 
under the pressure of 760 millimetres, weighs 1.97 grammes. 




Fig. 83. 



It was first liquefied by Faraday. At 0° it requires a 
pressure of 38.5 atmospheres, and at 31° (its critical tem- 
perature), 74 atmospheres. The apparatus which is now 
used for its liquefaction is represented in Fig. 83. It is 
composed of two reservoirs, A and B, communicating by 



CARBON DIOXIDE. 223 

the metallic tube i. furnished with a stop-cock at each end. 
The cylinders are made of heavy cast-iron, and are further 
strengthened by forged iron bands forced over their circum- 
ference. Each cylinder is movable on a horizontal axis. A. 
B is the generator ; into it are introduced 1800 grammes 
of sodium dicarbonate, and a cylindrical copper tube, D, 
containing 1000 grammes of ordinary sulphuric acid. The 
cylinder is then closed by a strong screw plug, and a few oscil- 
lating movements are given to it in order that the sulphuric 
acid may gTadually inin out upon the sodium dicarbonate. 
Carbon dioxide is disengaged and is liquefied by its own press- 
ure as it accumulates in the apparatus. By the effect of the 
chemical action the temperature is raised to 30 or 40°. and, 
communication being established between the two cylinders, 
the carbon dioxide distils rapidly into the receiver, the tem- 
perature of which is about 15°. 

The operation is repeated several times, that one or two kilo- 
gTammes of the liquid may accumulate in the receiver. A 
tube passes to the bottom of this vessel, and on opening the 
stop-cock which closes the superior extremity of this tube, a 
jet of the liquid is thi'own out with 
force : it is received tangentially in a 
metallic box. A. A' (Fig. S-i), having 
very thin sides. In this a portion 
of the oxide solidifies by reason of 
the gTeat depression of temperature 
produced by the change of another 
portion into the gaseous state. A 
glittering-white, flaky mass collects 
in the receiver, having the appear- 
ance of snow. This is solid carbon 
dioxide. It is a bad conductor of j_ 

heat and electricity, and can be ex- ^ ^.^^ g^ 

posed to the air for a few minutes 

before it disappears. In reassuming the gaseous form, it pro- 
duces an intense cold. If it be mixed with ether, the mixture, 
which is less porous and a better conductor of heat, can produce 
a lowering of temperature as gTeat as — 90°. By pouring it 
upon mercury, large masses of that metal may be frozen. 

Liquid carbon dioxide is now manufactured on a commercial 
scale, and sold in strong steel cylinders. It is colorless and 
mobile; has a density of 0.72 at -|-2T°, and 0.98 at — 8°. 




224 



ELEMENTS OF MODERN CHEMISTRY. 



This considerable difference between the densities is due to the 
enormous dilatation which the liquid undergoes between these 
limits of temperature. Indeed, ten volumes of liquid carbon 
dioxide at 0° occupy fourteen volumes at 30°. Hence the coeffi- 
cient of expansion of the liquid is superior to that of the gas. 
Carbon dioxide is incombustible, and extinguishes burning 
bodies. 

If carbon dioxide be poured from one vessel into another 
containing a lighted candle, it falls upon the flame like water, 

extinguishing it at once (Fig. 85). 
Lime-water poured into a jar 
of carbon dioxide becomes clouded, 
owing to the formation of insolu- 
ble calcium carbonate. 

These experiments permit the 
easy recognition of carbon dioxide 
from carbon monoxide. 

Carbon dioxide dissolves in its 
own volume of water at 15° under 
the normal pressure. If the press- 
ure be increased, the solubility of 
the gas is increased in the same 
proportion. Thus, under a press- 
ure of ten atmospheres one litre 
of water will dissolve ten litres of 
carbon dioxide ; but it must be remembered that under a press- 
ure of ten atmospheres these ten litres are reduced to one litre. 
Thus, one litre of water, which dissolves one litre of carbon 
dioxide at the ordinary pressure, dissolves also one litre under 
a pressure of ten atmospheres, and it may be said that water 
always dissolves its own volume of carbon dioxide, whatever 
may be the pressure. Water saturated with carbon dioxide 
under strong pressure, disengages a portion of the gas as soon 
as the pressure is removed. Such water is universally known 
and consumed in large quantities under the name of aerated 
water or soda water. 

The solution of carbon dioxide exercises a much more ener- 
getic solvent action upon certain substances than pure water. 
It dissolves calcium carbonate, forming a soluble dicarbonate ; 
it is even capable of dissolving calcium phosphate, transform- 
ing it into acid phosphate, which is soluble. 

Carbon dioxide is more soluble in alcohol than in water. 




CARBON BISULPHIDE. 225 

It is undecomposable by heat alone, but may be decomposed 
or reduced at higb temperatures by contact with bodies avid 
of oxygen. It is not reduced by hydrogen. With carbon the 
reduction takes place at a red heat, giving rise to the formation 
of carbon monoxide, the volume of which is double that of 
the carbon dioxide employed. 

CO^ + C = 2C0 

Carbon dioxide (2 vols.). Carbon monoxide (4 vols.). 

CARBON BISULPHIDE. 

CS2 

This body is prepared by passing sulphur vapor over incan- 
descent charcoal. In the arts, the operation is conducted in 
cylindrical, cast-iron vessels, filled with charcoal and heated to 
redness, into which sulphur is introduced. The carbon disul- 
phide distils, and is condensed in a suitable cooling apparatus. 

Carbon disulphide is a colorless, very mobile, and highly-re- 
fracting liquid. Its odor is usually strong and unpleasant, but 
is rather agreeable when the compound is perfectly pure. Its 
density at 15° is 1.271, and it boils at 46°. It is very inflam- 
mable, and burns with a blue flame, producing sulphur dioxide 
and carbon dioxide. 

CS^ -f- 30' = 2S0' + CO' 

Its vapor, mixed with oxygen, explodes when heated. 
Carbon disulphide corresponds in composition to carbon 
dioxide. 

CO^ carbon dioxide. 

CS' carbon disulphide. 

It is also analogous to the latter body in its chemical func- 
tions. While carbon dioxide combines with metallic oxides, 
forming carbonates, carbon disulphide combines with metallic 
sulphides, forming sulpho carbonates or thiocarbonates, 

CO' -f Na'O = Na'CO^ corresponding to H'CO' 

Sodium oxide. Sodium carbonate. Carbonic acid 

(hypothetical). 

CS' + Na'S = Na'CS^ corresponding to H'CS^ 

Sodium sulphide. Sodium sulphocarbonate. Sulphocarbonic acid. 

Sodium carbonate and sulphocarbonate possess the same con- 
stitution. By the action of strong acids they should give anal- 
ogous products: the one, carbonic acid, H'CO^; the other, 



226 ELEMENTS OF MODERN CHEMISTRY. 

sulphocarbonic acid, H^CS^ The latter body is indeed formed 
under such circumstances, but normal carbonic acid, if it exist, 
possesses no stability, and at once decomposes into carbon diox- 
ide and water. 

Carbon disulphide is employed in the arts in the manufac- 
ture of vulcanized caoutchouc, and as a solvent for caoutchouc 
in the fabrication of goods impermeable to water by the deposit 
of a thin layer of that substance. It is also employed as a 
solvent for, and in the extraction of, fats and oils. In the 
laboratory it is useful as a solvent for sulphur, phosphorus, 
iodine, oils, fats, etc. 

CARBON OXYSULPHIDE. 

Density compared to air 2.1046 

Density comiDared to hydrogen 30.4 

Molecular weight CSO =59.61 

This body was discovered by von Than in 1867. It is inter- 
mediate between carbon dioxide and carbon disulphide. 

COO carbon dioxide. 
CSO carbon oxysulphide. 
CSS carbon disulphide. 

Preparation. — It is prepared by decomposing potassium sul- 
phocyanate by dilute sulphuric acid. Potassium sulphate and 
sulphocyanic acid are formed, and the latter, in the presence 
of an excess of sulphuric acid and water, decomposes into am- 
monia and the gas carbon oxysulphide, which may be collected 
over mercury ; the ammonia remains combined with the sul- 
phuric acid in the form of sulphate. 

CSNH + H^O = NH^ + CSO 

Sulphocyanic acid. Carbon oxysulphide. 

Properties. — Carbon oxysulphide is a colorless gas, having 
an odor like that of carbon disulphide, but also recalling that 
of hydrogen sulphide. 

On contact with an incandescent body, even a match pre- 
senting a spark of fire, it takes fire, burning with a blue flame, 
and depositing sulphur if the supply of air be insufiicient. 
With one and a half times its volume of oxygen it constitutes 
an explosive mixture. 

2 volumes of carbon oxysulphide . . = CSO mixed with 

3 volumes of oxygen = 0^ yield 

2 volumes of carbon dioxide ....=: CO^ and 
2 volumes of sulphur dioxide . . . . = SO^ 



COMPOUNDS OF CARBON AND HYDROGEN. 227 

Water dissolves about its own volume of carbon oxysulphide, 
but the solution decomposes in a few hours, with the formation 
of hydrogen sulphide and carbon dioxide. 

CSO + H^O = CO^ + H^S 

Carbon oxysulphide is absorbed completely, but more slowly 
than carbon dioxide, by solutions of the alkaline hydroxides ; 
by a reaction analogous to the preceding, a sulphide and a 
carbonate are formed. 

COMPOUNDS OF CARBON AND HYDROaEN. 

These compounds are numerous and important. Carbon 
unites with hydrogen in different proportions, and the atoms of 
carbon and hydrogen may accumulate in considerable numbers 
in the molecules of their compounds. These combinations are 
called hydrocarbons or carbides of hydrogen. Hydrogen mono- 
carbide, or marsh gas, contains only one atom of carbon com- 
bined with four atoms of hydrogen ; its molecule is therefore 
represented by the formula CH*. In olefiant gas, or ethylene, 
two atoms of carbon are united with four atoms of hydrogen; 
in the volatile liquid known as benzene or benzol, which is ob- 
tained in large quantities from coal-tar, six atoms of carbon are 
combined with six atoms of hydrogen. Lastly, the molecule 
of oil of turpentine contains ten atoms of carbon and sixteen 
of hydrogen. 

Hence these substances give us the following formulas : 

CH* methane, or marsh gas. 
C^H* ethylene, or olefiant gas. 
C^H^ benzene. 
C'^H'^ turpentine. 

These examples, which might be indefinitely multiplied, show : 
1st. That the atoms of carbon unite in various proportions with 
the atoms of hydrogen to constitute the molecules of the hydro- 
carbons. 2d. That they accumulate in greater or less numbers 
to form molecules more and more complex, that is, containing 
an increasing number of atoms of carbon and hydrogen. 

All of these bodies must be considered among the organic 
compounds ; indeed, the latter are nothing more than the com- 
pounds of carbon, and carbon monoxide and dioxide may also 
be properly considered as the most simple organic combinations. 



228 



ELEMENTS OF MODERN CHEMISTRY. 



Hence if the most strictly rigorous method were adhered to, 
the description of the compounds of carbon and oxygen would 
be followed by that of all the other compounds of this element, 
that is, of all the organic compounds. However, for the pur- 
poses of study it is advantageous to treat the latter bodies 
separately, and they will be so considered in this work. The 
following experiments will expose some of the general proper- 
ties of the hydrocarbons which have been mentioned : 

1. If a lighted taper be applied to a jar of methane, which 
is also called marsh gas, because it is disengaged from the muddy 
bottoms of marshes, the gas takes fire and burns with a faintly 
luminous flame. 

2. If the same experiment be repeated with ethylene gas, 
which contains for the same proportion of hydrogen twice as 
much carbon as marsh gas, a highly luminous flame results. 

3. It is well known that benzene and turpentine take fire 
when lighted, and burn with bright flames ; but it is also known 

that their flames are smoky. 

The hydrocarbons are then 
combustible; and how could 
they be otherwise, since they 
contain only two combustible 
elements, carbon and hydro- 
gen? The products of the 
combustion are water and 
carbon dioxide, and the forma- 
tion of the latter gas may be 
proved by agitating the con- 
tents of the jars in which the 
combustion has taken place 
with lime-water; the latter 
immediately becomes milky 
by the precipitation of calcium 
carbonate. 

This combustion is more or 
less complete ; when the gas or 
vapor which burns contains a 
large amount of combustible elements, the oxygen of the air 
may not be present in suflicient quantity to burn them all, that 
is, to oxidize them completely. Under these conditions it is 
the hydrogen which is burned by preference, and the carbon 
partly escapes combustion. 




STRUCTURE OP FLAME. 



229 



A flame is a gas or vapor in combustion. This combustion 
is an oxidation, and it is the oxygen of the air which is the 
agent. In order that it may take place, it is generally neces- 
sary that the combustible gas shall be brought to a high tem- 
perature; but once commenced, the combustion continues of 
itself, because the heat disengaged by 
the oxidation is sufficient to maintain the 
phenomenon. But if a flame be suddenly 
cooled, the combustion is at once arrested. 

A flame may be cooled by depressing 
into it a piece of fine wire gauze. The 
incandescent gases cannot pass through 
the meshes of the gauze without being 
cooled by contact with the metal, which 
is a good conductor of heat. For this 
reason, no combustion takes place above 
the gauze (Fig. 86). 

If a piece of wire gauze be held over 
an escaping jet of gas, the latter may be 
ignited above the gauze, and will burn 
without the combustion being propagated 
to the gas below ; the gauze acts as a 
screen, separating the jet into two portions, 
the lower cold and invisible, the upper in 
combustion and luminous. 

Sir Humphry Davy made a happy ap- 
plication of these facts in the construction 
of the miner's safety-lamp. This is an 
ordinary lamp surrounded by a cylinder 
of wire gauze (Fig. 87). 

Such a lamp gives less light than one 
not protected by an envelope, but it re- 
moves the danger of explosions of fire- 
damp, for when an explosive mixture is 
formed in the galleries of a mine, the gas 
may penetrate to the interior of the lamp and take fire there, 
but the flame cannot pass through the cooling envelope of wire 
gauze. The safety-lamps are now constructed with the lower 
part of the cylinder of glass, so that there is no diminution in 
the amount of light given. 

As the oxidation of combustible elements is the source of 
heat, it is evident that the difi"erent parts of a flame cannot be 

20 




Fig. 



230 



ELEMENTS OF MODERN CHEMISTRY. 



uniformly hot, for the oxygen of the surrounding air cannot 
equally attain all portions. The exterior borders are the most 
intensely heated; they are surrounded by air, and constitute 
the seat of combustion. From them the heat is radiated not 
only externally, but also to the interior of the 
flame, where it produces interesting phenomena. 
These may be studied by analyzing a flame, 
that is, considering separately the difi"erent parts 
\^' of which it is composed. If the flame of a can- 
dle be examined, it will be found to present three 
distinct layers, or cones (Fig. 88). 

1. A dark central part, a, which surrounds 
'^ MA ^^^ wick. This is known as the obscure cone, 

or cone of generation; its temperature is not 
high. 

2. A luminous part, hh' , surrounding the ob- 
scure cone. This is the centre from which the 
lio'ht is emitted. It is known as the luminous 
cone, or cone of decomposition. 

3. An exterior envelope, cc', thin, and pro- 
ducing but little light, yellow towards the sum- 
mit, e, and bluish towards the base, dd'. It is the 
cone of complete combustion, and its temperature 
is the highest. 

It is easy to account for these phenomena. 
The material of the candle is melted by the heat 

Fig. 88. ^^ ^^ flame, the liquid is drawn up into the 
wick by capillarity, and arrives at the incan- 
descent summit. There it is decomposed, producing gases and 
vapors rich in carbon and hydrogen, and which rise around the 
wick, forming an irregular cone. The gaseous products consti- 
tuting this cone do not present the same composition through- 
out. They have been analyzed by H. Sainte-Claire Doville, 
by the aid of very ingenious processes. 

The obscure cone is formed of gaseous products holding in 
suspension finely-divided carbon, which has not yet arrived at 
incandescence. 

These products become heated on reaching the more central 
portions of the flame. Then the carbon, which is set free by 
the decomposition of gases rich in carbon, is brought to bright 
incandescence, but it is completely burned only when it reaches 
the exterior envelope, where the oxygen is in excess. A simple 



STRUCTURE OF FLAME. 



231 



experiments will demonstrate that the most luminous portion 
of the flame holds in suspension finely-divided and incandes- 
cent carbon. If a porcelain saucer be depressed into this 
portion, the carbon will be deposited on the vessel as soot. 

It is this solid and incandescent carbon which causes the 
luminosity of the flame. The flame of hydrogen, which con- 
tains only gaseous products, is pale. In the calcium or Drum- 
mond light it produces great brilliancy because a solid body, 
lime, is heated to bright incandescence. When the carbon 
suspended in a flame is in excess in proportion to the supply 
of oxygen, it is incompletely burned, and is carried into the 
air. The flame then smokes. 

At the base of the cone, carbon monoxide and methane, the 
first products of the decomposition of the candle, burn on con- 
tact with the air at dd' with a bluish flame. 

The luminosity of a flame is not necessarily due to the presence 
in it of solid matter. It depends very largely upon the temperature 
and the density of the burning gas. The flame of hydrogen, accord- 
ing to Frankland, is luminous when that gas is burned under strong 
pressure, and the flame of illuminating gas may be rendered non- 
luminous by diluting with an indifferent gas, such as nitrogen, and 
thus reducing the temperature- 
Illuminating gas is a mixture of hydrogen with various gas- 
eous hydrocarbons and a small proportion of carbon monoxide. 
It is manufactured by the destructive dis- 
tillation of bituminous coal. The aqueous 
products containing ammonia, and the 
tarry matters formed during the distilla- 
tion are condensed, and ih.Q gas is purified 
by washing with water and passage over 
slaked lime to remove sulphur and other 
impurities. 

Illuminating gas forms an explosive 
mixture with air, but if the mixture be 
burned as it is formed, the resulting flame 
will be almost colorless and will deposit 
no soot, the whole of the carbon coming 
in contact with sufficient oxygen for its 
complete combustion. These conditions 
are fulfilled in the Bunsen burner (Fig. 
89). In this burner, the force of the 
escaping gas-jet draws in air through holes near the jet in 
a wider tube, at the end of which the mixture is burned. 




Fig. 89. 



232 



ELEMENTS OF MODERN CHEMISTRY. 



GENEKAL NOTIONS UPON THE NON-METALS. 



THEORY OF ATOMICITY. 

From a consideration of the facts acquired in the study of 
the elements known as non-metals, we may deduce certain gen- 
eral consequences, and while looking back on the field over 
which we have passed, we may at the same time fix certain 
landmarks for the remainder of our course. 

The elements which we have studied are not alike in their 
aptitude to enter into combination, nor in the general characters 
of their compounds. In this respect, analogies and difi'er- 
ences have been established between them, and these have 
become the basis of a rational classification. Following the 
example of Dumas, we may arrange these elements in groups 
or families, uniting in the same group those which are related 
by their chemical functions. 



HYDROGEN. 


OXYGEN. 


NITROGEN. 


SILICON. 


HELIUM. 


FLUORINE. 


SULPHUR. 


PHOSPHORUS. 


CARBON. 


NEON. 


CHLORINE. 


SELENIUM. 


ARSENIC. 




ARGON. 


BROMINE. 


TELLURIUM. 


ANTIMONY. 




METARGON 


IODINE. 




BORON. 




XENON. 



The elements of the last group, which includes argon and 
helium, are characterized by their inability to form chemical 
compounds. 

In order to account for the chemical functions of the other 
non-metals — that is, for the parts which they play in their com- 
binations — we must first consider their hydrogen compounds. 



These constitute the following series 



HH 

Hydrogen. 

HCl 

Hydrochloric 
acid. 

HBr 

Hydrobromic 
acid. 

HI 

Hydriodic acid. 

HF 

Hydrofluoric acid. 



H^O 

Water, 

H^S 

Hydrogen 
sulphide. 

H^Se 

Hydrogen 
seleiiide. 

H^Te 

Hydrogen 
telluride. 



H^N 

Ammonia 

Hydrogen 
phosphide. 

H^As 

Hydrogen arsenide. 

H^Sb 

Hydrogen antimonido, 

H^B 

Hydrogen boride, 



H*Si 

Hydrogen silicide. 

H*C 

Hydrogen 
carbide. 



THEORY OF ATOMICITY. 233 

It is seen tliat the first four groups are characterized by the 
composition of their hydrogen compounds. While the bodies 
of the first group combine with hydrogen atom for atom, those 
of the second group require two atoms of hydrogen, those of 
the third three, and those of the fourth four, to form hydrogen 
compounds. Hence we may draw the conclusion that the atoms 
of these non-metals are far from being equivalent in their 
power of combination with hydrogen. 

The atoms of chlorine, bromine, and iodine are equivalent 
to each other in this respect, for each requires but one atom 
of hydrogen. 

The atoms of oxygen, sulphur, etc., are equivalent to each 
other, for each combines with two atoms of hydrogen. 

The atoms of nitrogen, phosphorus, arsenic, antimony, and 
boron are equivalent to each other, for each of them unites 
with three atoms of hydrogen. 

Lastly, the atoms of carbon and silicon are equivalent, for 
each can unite with four atoms of hydrogen. 

But, on the other hand, it is evident that the atoms of chlo- 
rine, oxygen, nitrogen and carbon are not -equivalent to each 
other, as regards their power of combination with hydrogen, 
since each of them unites with a difierent number of atoms of 
that body. 

In this respect it may be said that 

1 atom of chlorine is equivalent to 1 atom of hydrogen. 
1 atom of oxygen " 2 atoms " 

1 atom of nitrogen " 3 atoms " 

1 atom of carbon " 4 atoms " 

It is evident that the capacity of combination which resides 
in the atoms of simple bodies and by which they attract the 
atoms of hydrogen, is unequal. Leaving aside its intensity, 
this force is exerted in difi"erent degrees, for it determines the 
union of 1 atom of chlorine, oxygen, nitrogen, or carbon, with 
1, 2, 3, or 4 atoms of hydrogen. 

This number of hydrogen atoms is the measure of the degree 
of force which resides in the atoms, — of the capacity of combi- 
nation which they possess for each other. 

Hence we conclude that 

The atoms of chlorine and its associates are monatomic or univaletit. 
The atoms of oxygen " " diatomic or bivalent. 

The atoms of nitrogen " " triatomic or trivalent. 

The atoms of carbon " " tetratomic or quadrivalent. 

20* 



234 ELEMENTS OF MODERN CHEMISTRY. 

The capacity of combination which resides in the atoms, and 
which is exerted in such different manners according to the 
nature of the atoms, is called atomicity. Atomicity is the 
relative equivalence of the atoms; it is simple or multiple, and 
if we consider it in its first degree, we may say that the atoms 
of chlorine and the atoms of hydrogen are so constituted that 
a single atom of one attracts a single atom of the other. When 
they combine, they exchange in some manner a unit of satura- 
tion, and in the combination of chlorine and hydrogen two of 
these units of force are neutralized ; two units of saturation or 
two atomicities are exchanged: the atoms of chlorine and of 
hydrogen are univalent. 

The force which resides in an atom of oxygen is more com- 
plex. It attracts two atoms of hydrogen, and represents the 
second degree of capacity of combination, and we may say that 
in each atom of oxygen reside two atomicities, which are satis- 
fied and exchanged when this atom combines with two atoms of 
hydrogen. Hence, four atomicities are satisfied by the com- 
bination. 

Following the same reasoning, we consider that a triple capa- 
city of combination is active in an atom of nitrogen when this 
atom unites with three atoms of hydrogen ; and that six atom- 
icities are satisfied by the combination. 

Lastly, tetratomic carbon is provided with four atomicities, 
which are satisfied by the four atomicities which reside in four 
atoms of hydrogen. 

If this neutralization or exchange of two units of saturation 
be represented by a hyphen, we will have the following formulae : 



H-Cl 


H-O-H 


H 


H 


Hydrochloric acid. 


Water. 


1 


1 






N 


H-C-H 






/\ 


1 






H H 


H 






Ammonia. 


Hydrogen monocarbide. 



It is seen that in the formulae for water, ammonia and hydro- 
gen monocarbide, the polyatomic elements, oxygen, nitrogen 
and carbon, constitute, as it were, the nuclei around which the 
other atoms are symmetrically grouped. 

A great many other bodies present the same constitutions as 
the preceding ; it is evident that a given element in any com- 
pound may be replaced by another element having the same 
atomicity, without disturbing the equilibrium of the atomicities, 



THEORY OF ATOMICITY. 235 

Indeed, if we suppose the chlorine, oxygen, nitrogen, and 
carbon to be replaced by elements of corresponding atomicities, 
we will have the series of hydrogen compounds already con- 
sidered. All of the bodies which are classed together in the 
series belong to the same type. Each contains an equal num- 
ber of atomicities for the same number of atoms. 

According to the principle of substitution announced above, 
it is evident that the hydrogen in each of the hydrogen com- 
pounds under consideration may be replaced by another mon- 
atomic element, and the compounds thus formed will still belong 
to the primitive types. 

So considered, a great number of compounds possess the 
same constitution, — that is, the same molecular structure, — 
as hydrochloric acid, water, ammonia, and methane or hydro- 
gen monocarbide. Such are those arranged in vertical columns 



in the following 


table : 






Type HCl 


Type H20 


Type NH3 


Type 0H4 


Cl-Cl 


H-O-H 


K 


CI 


Free chlorine. 


Water. 


1 


1 






N 


Cl-C-Cl 






/\ 


1 






H H 


CI 




Potassium amide. 


Carbon tetrachloride. 


K-Cl 


Cl-O-Cl 


CI 


CI 


Potassium chloride. 


Hypochlorous oxide. 


1 


1 






P 


Cl-Si-Cl 






/\ 


1 






CI CI 


CI 




Phosphorus trichloride. 


Silicon tetrachloride. 


K-I 


H-O-K 


CI 


H 


Potassium iodide. 


Potassium hydroxide. 


1 


1 






Sb 


H-Si-H 






/\ 


1 


Ag-I 


Ag-O-Ag 


CI CI 


H 


Silver iodide. 


Silver oxide. Antimony trichloride, 


, Hydrogen silicide. 



All of these bodies belong to the respective types HCl, H'^O, 
NH^, CH*, the first three of which were established by Ger- 
hardt, and have their existence explained by the atomicity of 
the elements ; that is, by the varying equivalence of their atoms, 
measured, in the present examples, by the number of hydrogen 
atoms with which they combine. 

One atom of oxygen is equivalent to two atoms of hydrogen 



236 ELEMENTS OP MODERN CHEMISTRY. 

or two atoms of chlorine. Hence, in tlie preceding combina^ 
tions, two atoms of chlorine may be replaced by one atom of 
oxygen without changing the equilibrium of the atomicities. 
Thus, the oxides SiO^,CO^ correspond to the chlorides SiCl*, 
CCl*, and belong to the same type. The four atomicities of 
an atom of silicon or carbon are saturated by the four atomici- 
ties of two atoms of oxygen. 

The trichlorides of phosphorus and antimony, POP and SbCP, 
which will be found in the preceding table, require an impor- 
tant remark. They are not saturated with chlorine, and each 
may combine with two more atoms of that element, producing 
the compounds POP and SbCP. 

Thus, while phosphorus exhausts its power of combination 
with hydrogen in uniting with three atoms of that element in 
PH^, its capacity of combination with chlorine is only exhausted 
when it has combined with five atoms ; while it plays the part 
of a triatomic element in hydrogen phosphide, it is pentatomic 
in phosphorus pentachloride. 

From these facts it follows that it is often difficult to meas- 
ure in an absolute manner the capacity of combination which 
resides in an atom ; for that capacity varies according to the 
nature of the elements upon which it is exerted. Affinity is 
an elective force. A given element does not attract all of the 
other elements with equal facility ; it selects certain ones by 
preference, and neglects the others. With one, it may form 
but a single compound; with another, it may form several. 

The most important compound of nitrogen and hydrogen is 
ammonia, NH^, which cannot fix any more atoms of hydrogen. 
Saturated with hydrogen in ammonia, nitrogen manifests in 
contact with that element but three atomicities. But let am- 
monia be brought in contact with a body other than hydrogen, 
hydrochloric acid, for example, and it will combine with it, 
forming ammonia hydrochloride, or ammonium chloride. If 
its capacity of combination is exhausted for hydrogen, HH, it 
is not exhausted for hydrogen combined with chlorine, HCl. 
Thus, an atom of nitrogen possesses other affinities than those 
which it manifests for hydrogen in ammonia. While nitrogen 
is triatomic in ammonia because it is united with three mon- 
atomic atoms, it behaves as a pentatomic element in ammonium 
chloride. 

The parts which polyatomic elements play in their compounds 
may be expressed by accents marking the number of atomici- 



THEOUY OF ATOMICITY. 237 

ties or tlie quantivalence of the element, as shown in the 
following formulae : 

0"H^ X"'H' N-H*C1 F"CP P^CP C^'O"^ 

Water. Ammonia. Ammonium Phospliorus Phosphonis Carbon 
chloride. trichloride, pentachloride. dioxide. 

In these compounds, as has been remarked before, the poly- 
atomic elements form, as it were, the nuclei around which the 
other elements are grouped. This is an important idea, since 
it leads to the determination of the constitution of the mole- 
cules, that is, the arrangement of their atoms. The considera- 
tions just presented concerning the functions of the elements 
in compounds alone permit the resolution of this question; 
they alone lead to the discovery of the relations existing be- 
tween the atoms in theii' combinations, and to the determina- 
tion of their relative positions, in a word, to the revelation of 
the molecular structure. 

The following developments will demonstrate this fact. 

We will reconsider certain of the combinations above men- 
tioned, which have been taken as t3rpes. 

In water, an atom of diatomic oxygen fixes two atoms of 
hydrogen. One atom of oxygen can fix two atoms of any 
monatomic element, forming compounds belonging to the same 
type as water; but it cannot at the same time fix a monatomic 
element and a diatomic element. In other words, an atom of 
hydrogen in water may be replaced by an atom of chlorine, 
bromine, iodine, or potassium, but not by an atom of oxygen ; 
and if a second atom of the latter element be joined to the 
oxygen of water, it will be seen that there remains a free affin- 
ity which may be satisfied by hydrogen. Hydrogen dioxide 
would result. 

H-0"-H H-0"-0"-H 

Water. Hydrogen dioxide. 

Hence, we draw the conclusion that in hydrogen peroxide, 
the two atoms of oxygen are combined with each other, and 
that in uniting together each atom loses one atomicity, the two 
others being satisfied by hydrogen. 

The same considerations are applicable to the compounds of 
chlorine and oxygen. 

Hypochlorous acid may be regarded as composed of an atom 
of chlorine united to the group hydroxyl. 
Cl-0"-H = Cl(OH)' 

Hypochlorous acid. 



238 ELEMENTS OF MODERN CHEMISTRY. 

In this compound the chlorine exchanges one unit of satu- 
ration with the oxygen of the group OH, just as it exchanges 
one with hydrogen in hydrochloric acid: it is monatomic or 
univalent. In chloric acid it is combined with two atoms of 
oxygen and one group, OH. It exchanges 4 atomicities with 
oxygen, and one with the group OH : 

Cl^O^-^OH)' 

Chloric acid. 

Chlorine thus manifests 5 atomicities in chloric acid ; but it 
has 7 in perchloric acid. 

Cl-'O^(OH)' 

Perchloric acid. 

Without dwelling on these considerations, we will take one 
more example. 

In hydrogen phosphide, one atom of phosphorus is combined 
with three atoms of hydrogen ; it manifests but three atomici- 
ties, and these could not neutralize those which reside in three 
atoms of oxygen, since the latter possess six atomicities. If, 
then, three atoms of diatomic oxygen were united with one 
atom of triatomic phosphorus, it is clear that three affinities 
would remain free, one in each of the three atoms of oxygen. 
In phosphorous acid, these three affinities of the oxygen atoms 
are satisfied by three atoms of hydrogen. We may suppose 
that in the molecule of this compound, the phosphorus is the 
nucleus around which are grouped three atoms of oxygen, each 
of which is joined also to one atom of hydrogen. 

This atomic grouping is indicated in the following formulae : 

H OH 

I I 

P P 

/\ ^ 

H H HO OH 

Hydrogen phosphide. Phosphorous acid. 

This hydrogen, combined with the oxygen in all of the oxy- 
gen acids, plays invariably the same part: it saturates the one 
atomicity which remains free in one atom of oxygen. The 
oxygen thus combined with an atom of hydrogen, has lost one 
of its atomicities by the fact of this combination ; it still retains 
one in the group OH, which represents, as it were, water less 
one atom of hydrogen. 

HOH — H = (OHy 



THEORY OF ATOMICITY. 239 

This group is named hydroxyl, and it is evident that, 
although it cannot exist by itself, it may play the part of a 
monatomic element, for it retains one free atomicity. It may 
then replace a monatomic element, such as hydrogen or chlo- 
rine. Indeed, it plays an important part in the constitution of 
acids. 

If we consider the examples which have already been dis- 
cussed, we will notice that it is this hydroxyl which, by com- 
bining with an element or group of elements capable of forming 
acids, confers upon them the characters of acids. So consid- 
ered, hypochlorous acid is formed by the union of hydroxyl 
with an atom of chlorine. 

Cl(OH)' 

Hypochlorous acid. 

Sulphuric acid is formed by the union of two hydroxyl groups 
with sulphurous oxide, and represents in a manner sulphuryl 
chloride in which the two atoms of chlorine are replaced by 
two hydroxyl groups. 

Sulphuryl chloride. Sulphuric acid. 

Phosphorous acid is formed by the union of three hydroxyl 
groups with one atom of phosphorus. 

(Cl f(OH)' 

F" i Cl F" ] (OH)' 

(01 ((OH)' 

Phosphorus trichloride. Phosphorous acid. 

Lastly, phosphoric acid results from the union of three hy- 
droxyl groups with one atom of phosphorus already combined 
with one atom of oxygen (phosphoryl). 

( 01 f (OH)' 

0"P'^C1 0"P'^(OH)' 

(Cl ((OH)' 

Phosphoryl trichloride. Phosphoric acid. 

Such, according to the theory of atomicity, are the relations 
existing between the atoms of certain acids ; such, in other words, 
is the constitution of these acids. It would be easy to extend 
these considerations to other bodies, but the examples we have 
chosen are sufficient to indicate the importance of the idea of 
atomicity, when it is applied to the discovery and definition of 



240 ELEMENTS OF MODERN CHEMISTRY. 

the part played by eacli element in a given compound. By 
supposing tlie capacities of combination of cblorine, oxygen, 
sulphur, and phosphorus to be known, we have been able to 
follow these bodies in their most important combinations, we 
have seen how they attract and group around themselves other 
elements. We have thus been able to penetrate the atomic 
structure of the molecules, and have built up as it were the 
molecular edifice. It must be remembered, however, that the 
preceding formulae do not in any manner represent the real 
positions of the atoms in space. Their sole object is to indi- 
cate the points of attachment of the affinities, and consequently 
the mutual relations between the atoms. 



CHEMICAL ENERGY— THERMO-CHEMISTEY. 

The study of the elements and compounds already described 
has shown that combination is usually accompanied by a more 
or less intense development of energy, while in some cases 
energy is developed by decomposition. W;e have seen that 
many compounds are dissociated or separated into their elements 
by temperatures more or less elevated, and it is not difficult to 
understand that the amount of energy developed or absorbed 
in the formation of a compound, is the exact measure of the 
energy required or developed in its decomposition. 

The determination of the precise amount of energy developed 
or absorbed in any chemical reaction is the object of thermo- 
chemistry. In order to simplify and harmonize results for com- 
parison, the kilogramme degree is selected as the unit of energy, 
representing the quantity of heat necessary to raise the tem- 
perature of one kilogramme of water through one degree centi- 
grade. This unit is termed a calorie, and the heat of formation 
or decomposition of a compound is expressed by the number 
of calories produced by the formation or decomposition of one 
molecule of the substance, the atom of hydrogen being supposed 
to weigh one gramme. Thus the heat of formation of carbon 
dioxide will be the number of calories produced by the perfect 
combustion of twelve grammes of carbon. When practicable, 
the heat of formation is determined by the energy of combus- 
tion. As a general formula, we may consider that the combining 
atoms possess a quantity of energy in some form, chemical or 



CHEMICAL ENERGY — ^THERMO-CHEMISTRY. 241 

physical, which quantity we may call w. The product of the 
reaction will possess m ± n energy, ± n being the quantity 
of energy disengaged by the reaction. 

It has been found that the amount of energy developed by 
the formation of any compound from its elements is precisely 
the same whether the body is formed at once or by several 
stages (Hess). Thus, the heat of formation of CO^ is the 
same whether it be formed by 

C -f 0^ = C0^ or by C + = CO and CO + = C0= 

In the oxidation of a combustible compound which has been 
formed with disengagement of energy, less heat should be pro- 
duced than by the direct oxidation of the constituent elements, 
since part of their atomic energy has already been disengaged 
by their combination. Thus, the energy of formation of CH* 
should be represented by the difference between the heat pro- 
duced by the combustion of CH*, and that produced by the 
combustion of C plus that of H* (H = 1 gramme). The 
energy of formation of CO will be the difference between the 
energy of combustion of C and that of CO. 

Direct and indirect methods of reasoning of this kind have 
enabled the calculation of the energy of formation of a large 
number of compounds. 

The physical state of the reacting bodies and of the product 
is necessarily an important factor in therm o-chemical consider- 
ations. If the product be gaseous while the reacting bodies 
be liquid or solid, a certain amount of energy will be required 
to maintain the matter in the gaseous form, and this quantity 
must be calculated and added to that actually resulting from 
the reaction. If, on the contrary, the bodies entering into 
combination be liquid or gaseous while the result is solid, the 
direct energy of combination will be lower than the heat de- 
veloped by the reaction. 

While the laws governing chemical energy are as yet unde- 
veloped, it is not difficult to understand the cause of the phe- 
nomena in which heat is disengaged or absorbed. We must 
believe that the atoms of any element are endowed with motion, 
and chemical energy then becomes atomic motion. If the 
atomic motion be arrested, the energy appears as heat, molecu- 
lar motion, or in some other form. When two elements 
manifest energetic affinities for each other, it is because their 
atoms are moving in such a manner that a portion of the 
L ^ 2i 



242 ELEMENTS OF MODERN CHEMISTEY. 

atomic motion may be mutually arrested ; this atomic energy 
is then transformed into heat energy or molecular motion. 

While all chemical action must be referred to atomic motion, 
the manner of that motion cannot at present be fully under- 
stood. Atomic energy, that is, affinity, must be a function of 
temperature, since the atomic vibrations of the elements may 
be so varied by an absorption of energy from external sources 
that, on one hand, the motions of atoms manifesting little 
affinity for each other may be so harmonized that combination 
must take place, and, on the other, the harmonious movements 
of unlike atoms may be rendered so incompatible that those 
atoms will separate, finding conditions of more stable equilib- 
rium in molecules of the elementary substances. 

In this manner we can readily interpret those cases in which 
decomposition is attended by a development of energy, as with 
hydrogen dioxide, nitrogen iodide, and many other compounds. 
In the formation of nitrogen iodide by the action of ammonia 
on iodine (page 155), ammonium iodide also is formed. 

4:NW -f 3P = NP -1- 3NH*I 

Ammonium iodide is formed with disengagement of energy, 
but in the above reaction that energy does not become apparent ; 
the liquid does not become warm ; the energy which disappears 
from the atoms in the ammonium iodide is transferred to the 
atoms of nitrogen and iodine, and enables them to combine, 
forming nitrogen iodide. These atoms then possess greater 
energy than when in molecules of nitrogen and iodine, and on 
the least disturbance of the unstable equilibrium the nitrogen 
iodide is decomposed ; the atoms of nitrogen combine, forming 
molecules of nitrogen, and the atoms of iodine form molecules 
of iodine. The energy furnished by the formation of ammo- 
nium iodide then becomes external explosively. 

A compound which is formed from its elements with libera- 
tion of energy is called an exothermic compound, while one 
which is similarly formed with absorption or disappearance of 
energy is called an endofhermic compound. All explosive com- 
pounds are endothermic. 

As a general rule, in any chemical equation the sum of the 
energies developed in the formation of the compounds pro- 
duced must be greater than the sum of the energies developed 
in the formation of the substances reacting. Unless energy 
be supplied the reaction is otherwise impossible (Berthelot). 



METALS. 



The metals are elements which are good conductors of heat 
and electricity, and are endowed with a peculiar lustre, which 
is called the metallic lustre. This definition, it will be ob- 
served, is founded upon certain physic-al characters rather than 
upon chemical properties. It is unsatisfactory and wanting in 
exactness, for it is applicable to bodies which are properly con- 
sidered as metalloids. Such is antimony, which has already 
been described, and bismuth, which should be placed beside 
antimony. Indeed, the distinction between the metals and 
non-metals is not so well marked that a line which shall sepa- 
rate these two classes of simple bodies may be sharply drawn. 

Physical Properties of the Metals. — These will be found 
in the table on page 244, but the indications there given may 
be completed by certain other developments. 

The metals are opaque, but their opacity is not absolute. 
A sheet of gold-leaf pressed out between two plates of glass 
allows the passage of a green light. 

Gold possesses a brilliant lustre and a yellow color, but it 
loses this lustre when it is reduced to very fine powder. When, 
however, this powder is rubbed with a hard body, when, for 
example, it is triturated in an agate mortar, or passed under 
the burnisher, it acquires a certain degree of cohesion, and 
again assumes its lustre. 

It is thus with all the metals. They lose their metallic lustre 
when finely divided and reassume it on burnishing. 

The yellow color of gold is not its true color ; the rays which 
reach the eye are the result of but one reflection, but if light 
be successively reflected from ten surfaces of gold, the metal 
will appear of a bright-red color. Under the same circum- 
stances, copper will appear scarlet, zinc indigo, iron violet, and 
silver pure yellow (B. Prevost). 

Most of the metals may be crystallized. Bismuth is the 
most striking example. If a few kilogrammes of pure bismuth 
be fused, and the liquid mass be allowed to cool slowly, the 

243 



244 



ELEMENTS OF MODERN CHEMISTRY. 



!S 2 AS a 



rt ° « a &.2 

ja _^ « £ ° 5 ' 



cra&H < 



I I I I o a a 
:^ o S 5 ^ <1 S 



Oh S O O M 5 6 H 



g- : 



05 05 O (N 



o o .2 -S o .2 .2 .2 S 



oSS^msSoSSiJ 



■■3 -o 



r-l f- r-1 1-; O O 

o o o o c> o 



^^ o 00 CO -* ■* ^ 

i i i i s i i 

o o a <6 o o o 



?5 O tSl O (X, 



fl S -B 2 s -^ *§ 
a _ a oj o .3 S 
H cc ^ ;^ O &< J 



o « 



SS2 



.-S o o .S .S 









3 

(L, cB El cq ►.:? o 



I a 



. 21.70 
. 21.15 
. 21.40 
. 19.35 
-42° 14.40 
'^ . 13.59 
. 11.80 
. 11.33 
. 10.57 
. 9.82 


. 8.79 
, 8.60 
. 7.79 
. 7.79 
. 7.25 
. 7.29 
. 7.20 
. 7.01 
. 6.86 
. 6.71 
. 2.56 
. 0.97 

. 0.59 


5 ai >> .2 1^5 





1 il 






O N <5 <; t» Oi h5 



GENERAL PROPERTIES OF METALS. 



245 



metal will solidify first next to tlie walls of the vessel and on 
tlie surface, where it is most cooled. If, in a little while, the 
crust which covers the still liquid metal be pierced, and the 
latter be poured out, the whole of the interior of the vessel 
will be found covered with magnificent crystals, arranged in 
hopper-like pyramids, and presenting brilliant, rainbow-like 
colors. 

Other metals, such as copper, lead, antimony, tin, silver, and 
gold, may be crystallized under certain conditions. Some of 
the metals are found crystallized in nature. 

Those metals which may be beaten or rolled into thin laminae 
are said to be malleable. AA (Fig. 90) represent two steel 




Fig. 90. 

rollers capable of moving on their axes in opposite directions. 
A plate of metal engaged between them will be drawn in, and 
the rolled sheet will pass out on the other side with a uniform 
thickness equal to the distance between the two rollers. By 
diminishing this distance more and more by means of the 
screws BB, the sheet may gradually be reduced in thickness. 

Metals which may be drawn out into wires are said to be 
ductile. The wire-drawing machine is represented in Fig. 
91. It consists of a steel plate, ff, firmly fixed in the up- 
rights CC, which are themselves solidly attached to a bench. 
The plate is pierced with a series of holes regularly decreasing 
in diameter. The wire is drawn from the bobbin A, through 
the holes and around the cylinder B, which is moved by power. 

That a metal may be drawn into fine wires, it is necessary 
that it shall olfer a certain resistance to rupture. This is called 
the tenacity of the metal. It is measured by suspending weights 

21* 



246 



ELEMENTS OF MODERN CHEMISTRY. 



at the extremities of wires of the same diameter. The metals 
exhibit every degree of fusibility. Mercury is liquid at ordi- 
nary temperatures, while osmium cannot be melted in the 
oxyhydrogen flame. Some metals, such as mercury, potassium, 
zinc, are readily distilled ; others are scarcely volatilized at the 
highest attainable temperatures. 

Chemical Properties of the Metals. — The metals combine 
with each other and with the metalloids, the energy with which 
these combinations take place being very variable. In general, 




Fig. 91. 



the metals having the strongest affinities are those known as the 
alkaline metals, because they are obtained from the alkalies. 
Such are potassium and sodium. 

All the metals combine directly with chlorine. The chlorides 
thus formed do not all possess analogous compositions ; they con- 
tain for one atom of metal a varying number of chlorine atoms. 

A similar remark applies to the oxides and sulphides formed 
by the union of oxygen and sulphur with the metals. The 
power of combination of the latter with chlorine, sulphur, oxy- 
gen, etc., is far from being the same. In other words, the atoms 
of the metals combine unequally with the atoms of chlorine, 
oxygen, etc. ; hence it follows that the atomic composition of 
the bodies thus formed is different. If the metals be compared 
together in this respect, analogies and differences will be estab- 
lished between them, which become the basis for a rational 
classification. Those metals which form compounds having 



EXTRACTION OF METALS. 247 

analogous atomic constitutions are put into tlie same group. 
Such principles as these have guided us in the classification of 
the non-metals, and we will apply them to the metals as soon as 
we have acquired a general knowledge of their compounds. 

K'atiiral State and Extraction of the Metals. — Certain 
metals are found in nature free from all combination. It is 
thus that gold, silver, copper, bismuth, etc., are met with in 
the native state. 

More often the metals are found combined with oxygen, sul- 
phur, or other non-metals. The natural sulphides are numerous 
and abundant : those of silver, copper, mercury, lead, and zinc 
constitute the minerals from which these metals are ordinarily 
extracted. 

Iron and tin are obtained from their oxides, which are found 
in nature. 

The metals are often found in saline combinations, in the form 
of chlorides, carbonates, sulphates, phosphates, and silicates. 

We can only indicate here in a very general manner the 
methods by the aid of which the metals are extracted from 
their combinations. 

If a metal is to be obtained from its oxide, the latter is 
generally reduced by carbon at a high temperature. A num- 
ber of oxides resist the reducing action of carbon at the 
highest temperatures attainable by the combustion of that 
element in the ordinary furnaces ; with few exceptions, how- 
ever, they will give up their oxygen to carbon when sub- 
jected to the intense heat of the arc in the electric furnace 
(see page 210). Some of the rarer metals have been obtained 
in this manner. 

Certain oxides reducible by carbon do not yield pure metal by 
such reduction, as the metal combines with part of the carbon, 
forming a carbide from which removal of the carbon is difficult 
or even impossible. In such cases reduction of the oxide may be 
accomplished by a more oxidizable metal : thus manganese and 
chromium oxides may be reduced by aluminium or magnesium. 

If the ore be a sulphide, it is first roasted, that is, heated in 
contact with the air. The oxygen of the air then acts upon 
the sulphur, which is disengaged in the form of sulphur di- 
oxide, and upon the metal, which remains in the form of oxide ; 
the latter is afterwards reduced by carbon. 

The metals are sometimes obtained from their chlorides by 
heating the latter with sodium, magnesium, aluminium, or other 



248 ELEMENTS OF MODERN CHEMISTRY. 

metal which will combine with the chlorine, forming the cor- 
responding chloride. 

Electrolysis of salts, either in aqueous solution or in a state 
of fusion, is now advantageously employed for the extraction 
of metals like copper, nickel, aluminium, and magnesium. 

ALLOYS. 

The combinations of the metals with each other are called 
alloys ; amalgams are the alloys formed by mercury. 

If a small quantity of mercury be heated in a crucible or a 
capsule, and a morsel of sodium be thrown into it, the latter 
dissolves instantly ; and by employing the proper proportions 
of mercury and sodium, the alloy may be obtained in crystals 
possessing a definite composition. 

Crystalline combinations of zinc and antimony are known. 
The most interesting has the composition Sb^Zn^ 

It is necessary to state that more generally the alloys do not 
present the characters of definite compounds. Many metals 
seem to alloy with each other in all proportions, forming mix- 
tures which are more or less homogeneous ; but this is only in 
appearance, and it must be admitted that one or more com- 
pounds exist in such a mixture, remaining dissolved in each 
other, or mixed with the excess of one of the metals. Such a 
mixture would form a sensibly homogeneous mass, especially 
when the molten mixture had been suddenly cooled. But if 
the cooling be slow, it may happen that the less fusible definite 
compounds separate from the mixture in the crystalline form, 
leaving the more fusible compounds which still remain liquid. 
Such a separation often takes place in large masses of melted 
alloys which are allowed to cool slowly. The process is called 
liquation^ and it may be readily conceived that the alloys so 
cooled are far from homogeneous in composition after their 
solidification. 

Conversely, when a mass composed of a mixture of metals 
and alloys is slowly heated, the more fusible assume the liquid 
state first, and separate from the others. 

This difference between the fusing-points of the various defi- 
nite compounds which may exist in an alloy is taken advantage 
of in the arts for their separation. 

Alloys are generally more fusible than their component 
metals. Thus, there is an alloy which melts at about 66° j 



ALLOYS. 



249 



and contains bismuth, 4 parts ; lead, 2 parts ; tin and cadmium, 
each 1 part. It is known as Wood's fusible metal. 

The following table gives the composition of some of the 
more important alloys : 



Gold coin (United States, France, 
Germany) 



Gold coin (Great Britain) . . 

Gold jewelry i 

Silver coin (United States) . 
Silver coin (Great Britain) . 
Silverware (sterling silver) . 

Bronze medals ..... 



Gun-metal . . . 
Bell-metal . . . 
Speculum-metal . 
Aluminium bronze 
Manganese bronze 
Red brass . . . 
White brass . . 



German silver 
Type-metal 

Britannia-metal 



Hard pewter . 
Soft pewter 
Plumbers' solder 



{Gold 900 

1 Copper 100 

f Gold 916.6 

1 Copper 83.4 

I Gold 750-920 

I Copper 250-80 

{Silver 900 

I Copper 100 

I Silver 925 

I Copper 75 

I Silver 925 

I Copper 75 

f Copper 93.5-95 

^ Tin 6-4 

( Zinc 0.5-1 

{Copper 100 

(Tin 10 

f Copper 78 

iTin 22 

f Copper 67 

ITin 33 

I Copper 90-95 

I Aluminium 10-5 

I Copper 90 

\ Manganese 10 

/Copper 90 

\ Zinc 10 

f Copper 65 

I Zinc 35 

{Copper 50 
Zinc 25 
Nickel 25 

I Lead 80 

I Antimony 20 

("Tin 

J Antimony .... 

j Bismuth 

[ Copper 

(Tin 

I Lead 

fTin 

I Lead 

I Tin 

1 Lead 



100 
8 
1 

4 
92 

8 
82 
18 
66 
33 



1 The proportion of gold in jewelry is expressed in carats, which signifies 
twenty-fourths. Thus, pure gold is twenty-four carats fine, while eighteen- 
carat gold contains eighteen twenty-fourths gold and six twenty-fourths 

of basfir allnv. 



of baser alloy. 



250 ELEMENTS OF MODERN CHEMISTRY. 



METALLIC OXIDES AND HYDROXIDES. 

Formation of Metallic Oxides. — The metals absorb oxygen 
with very unequal energy. Many of them become oxidized 
when exposed to the air at temperatures more or less elevated. 
In this respect it is important to distinguish the action of dry 
air from that of moist air. 

Potassium is the only metal that absorbs dry oxygen at ordi- 
nary temperatures. All of the other metals, with the excep- 
tion of silver, gold, and platinum, only become oxidized in the 
air at very high temperatures. Melted lead absorbs oxygen. 
Mercury becomes oxidized at about 350° ; copper at a dull-red 
heat. 

The combination often takes place with the production of 
luminous heat. Iron burns in oxygen, but it is necessary that 
the metal be first heated to bright redness that the combustion 
may take place. 

However, the finely-divided iron that is obtained by reducing 
oxide of iron in a current of hydrogen at a comparatively low 
temperature, will take fire when exposed to the air at ordi- 
nary temperatures. It is pyrophoric, and the fine state of 
division of the metal favors the oxidation. If the powder be 
projected into the air, each particle takes fire and burns with a 
bright flash. 

A bright sheet of iron will indefinitely preserve its brilliant 
surface in dry air, but if a drop of water be placed upon it, or 
if it be exposed to the action of a moist atmosphere, rust makes 
its appearance in a short time. This rust is ferric hydrate, 
for the metal has at the same time absorbed oxygen and 
water. 

It is generally admitted that it is the oxygen of the air dis- 
solved in the water that first fixes upon the metal, and that 
the combination is favored by the presence of carbon dioxide. 
However it may be, the spot of rust once formed constitutes a 
Voltaic couple with the iron itself, and the current so estab- 
lished decomposes the water. The oxidation then proceeds 
rapidly, the oxygen of the decomposed water combining with 
the metal. 

It is possible that hydrogen dioxide may play a part in oxi- 
dations ; it may be formed as a secondary product during the 



METALLIC OXIDES AND HYDROXIDES. 251 

decomposition of the water, and fix directly upon the metals, 
converting them into hydroxides (Weltzien). 

2Fe + 3ffO^ = 2FeO^H3 

Iron. Hydrogen dioxide. Ferric hydroxide. 

Mg -f- H^O^ = MgO^H^ 

Magaesium. Magnesium hydroxide. 

Indeed, the oxidation of metals in moist air always produces 
hydroxides, and not oxides. 

Composition and Classification of the Oxides. — It has 
already been remarked that the metals differ as to the number 
of oxygen atoms with which they combine ; besides this, the 
same metal may form several compounds with oxygen, con- 
stituting different degrees of oxidation. Hence the oxides 
present different compositions, and the differences exercise a 
marked influence upon the properties of the compounds. 

1. Certain oxides present the same atomic constitution as 
water. Two atoms of metal are combined with one atom of 
oxygen. 

Ag^O silver oxide. 
Cu^O cuprous oxide. 
Hg^O mercurous oxide. 
Au^O aurous oxide. 
TPO thallous oxide. 

2. One atom of certain metals can combine with one atom 
of oxygen ; the oxides of the general formula MO result. 

BaO barium oxide. 
SrO strontium oxide. 
CaO calcium oxide. 
MgO magnesium oxide. 
MnO manganous oxide. 
FeO ferrous oxide. 
ZnO zinc oxide. 
PbO lead oxide. 
CuO cupric oxide. 
HgO mercuric oxide. 
SnO stannous oxide. 

The metallic oxides containing but one atom of oxygen are 
generally energetic bases ; that is, they react energetically with 
the acids, forming salts. 

3. The sesquioxides are those which contain two atoms of 
metal and three atoms of oxygen. Such is antimony oxide, 
that has already been studied ; the oxides of bismuth, gold, etc., 
present an analogous composition. 



252 ELEMENTS OF MODERN CHEMISTRY. 

Sb^O^ antimony sesquioxide. 
Bi^QS bismuth sesquioxide. 
Au^QS gold sesquioxide. 

Fe^QS ferric oxide. 
Mn^QS manganic oxide. 
Cr^QS chromic oxide. 
Al^QS aluminium oxide. 

4. A large number of oxides contain two atoms of oxygen. 

Ba02 barium dioxide. 
SrO^ strontium dioxide. 
Mn02 manganese dioxide. 
PbO^ lead dioxide. 
Sn02 stannic oxide. 

The first four are incapable of uniting with acids to form 
corresponding salts. With hydrochloric acid, they yield either 
hydrogen peroxide or chlorine. 

BaO'^ + 2HC1 = BaCP + H^O^ 

MnO^ + 4HC1 = MnCP + 2H20 + CP 

"When manganese dioxide is heated with sulphuric acid oxygen 
is disengaged, and manganous sulphate is formed. 

H^SO* + MnO^ = MnSO* -f H^O + 

Sulphuric acid. Manganese dioxide. Manganous sulphate. 

As to stannic oxide, it is the anhydride of a metallic acid. 
SnO^ -f H^O = H^SnO^ 

stannic acid. 

5. The oxides which contain three atoms of oxygen possess 
acid characters still more marked than stannic oxide. Chro- 
mium trioxide, CrO^ is well known, and manganic and ferric 
anhydrides would present analogous compositions. 

6. There is a class of oxides still more complex than the 
preceding ; they can be regarded as formed by the union of 
two oxides, and they have been named saline oxides. Such are 

Ferroso-ferric oxide Fe^O* = FeO + Fe^O^, or magnetic oxide of iron. 
Manganoso-manganic oxide Mn^O* = Mn^O^ -f MnO, or red oxide of 

manganese. 
Diplumboso-plumbic oxide Pb^O* = PbO^ + 2PbO, or red oxide of lead. 

The first two contain one molecule of a sesquioxide, combined 
with one molecule of a monoxide ; the last, one molecule of a 
dioxide and two molecules of a monoxide. 



METALLIC OXIDES. 



253 



Chemical Properties of the Oxides. — Some of the oxides 
are fixed, that is, undecomposable by heat; others lose the 
whole or a part of their oxygen at temperatures more or less 
elevated. The oxides of the noble metals, such as silver, gold, 
and platinum, are decomposed by heat alone into metal and 
oxygen. We have seen that mercuric oxide is decomposed by 
a dull-red heat. Many of the oxides that contain two or three 
atoms of oxygen lose a part of the latter element when heated 
to redness. Such are the dioxides of manganese, lead, and 
barium. 

The oxides containing but one atom of oxygen are among 
the most stable. Some of them absorb oxygen when they are 
heated in contact with air, forming higher oxides. Among 
these are the monoxides of manganese, iron, lead, and tin. 

Hydrogen reduces the greater number of the oxides at tem- 
peratures more or less elevated ; water is formed, and the metal 
is set at liberty. 

If a current of dry hydrogen be passed over ferric oxide 
heated in a glass bulb (Fig. 92), the oxide is reduced, and a 




black powder is obtained which is finely divided and pyropho- 
ric iron. Vapor of water escapes at the same time by the 
drawn-out point of the bulb. 

Fe^O' + 3H^ = 3H^0 -f 2Fe 

Ferric oxide. Iron. 

22 



254 ELEMENTS OF MODERN CHEMISTRY. 

The ferric oxide may be replaced by cupric oxide, CuO. If 
this oxide be heated in a current of hydrogen, it is reduced, 
and the action is so energetic that it gives rise to the produc- 
tion of light and heat. 

Carbon reduces the greater number of the oxides with for- 
mation of either carbon dioxide or monoxide. It is even more 
energetic in its action than hydrogen, for it decomposes oxides 
which are irreducible by the latter element, such as those of 
potassium and sodium. The various oxides require for their 
reduction more or less heat, according to the degree of energy 
with which they retain their oxygen. If the reduction be 
difficult, a high temperature is required, and carbon monoxide 
is formed; otherwise carbon dioxide is the product. The 
oxides of calcium, barium, strontium, and aluminium are not 
reducible by carbon, except at the high temperature of the 
electric arc. 

A small quantity of cupric oxide may be reduced by char- 



FiQ. 93. 

coal by heating the mixture in a glass tube by the aid of a 
spirit-lamp (Fig. 93). Carbon dioxide is disengaged. 

2CuO + C == 2Cu + CO^ 

Cupric oxide. Copper. 

But to reduce zinc oxide by charcoal, the mixture must be 



METALLIC OXIDES. 



255 



heated to bright redness in a clay or u'on retort, and in this 
case carbon monoxide is evolved, 

ZnO -f- C =: Zn -I- CO 

Zinc oxide. Zinc. 

Chlorine decomposes nearly all of the oxides at a high tem- 
perature. It drives out the oxygen and combines with the 
metal, forming a chloride. Some of the oxides are in-educible 
by carbon, and resist also the action of chlorine. Such an 
oxide is aluminium oxide, or alumina. But if these oxides 
be submitted to the simultaneous action of chlorine and carbon 
at a high temperature, they are converted into chlorides, and 
carbon monoxide is disengaged. 

An intimate mixture of alumina and charcoal may be intro- 
duced into a porcelain tube, BB (Fig, 94), which is heated to 




Fig. 94. 



bright redness, and a current of dry chlorine then passed 
through. In this case, carbon monoxide is disengaged, while 
aluminium chloride is formed and volatilizes and may be con- 
densed in a cooled receiver. 

Sulphur decomposes all of the oxides except alumina and its 
analogues. The reaction takes place at a high temperature, 
and gives rise to the formation of a sulphide and sulphur di- 
oxide, or a sulphide and a sulphate if the latter be not decom- 
posable by heat. 



256 ELEMENTS OP MODERN CHEMISTRY. 

If sulphur be heated with cupric oxide, cupric sulphide is 
formed and sulphur dioxide is evolved. 

2CuO + 3S = 2CuS + SO^ 

Cupric oxide. Cupric sulphide. 

However, if calcium oxide (lime) or lead oxide, PbO, be 
heated with sulphur, a sulphate and a sulphide are formed. 
4CaO + 2S''' = 3CaS + CaSO* 

Calcium oxide. Calcium sulphide. Calcium sulphate. 

Action of Water upon the Oxides — Metallic Hydroxides 
and Acids. — If some fragments of barium oxide (baryta) be 
sprinkled with cold water, an energetic reaction immediately 
takes place. The water unites with the metallic oxide with so 
much energy that the heat disengaged is sufficient to convert 
a portion of the water into vapor. The barium oxide is con- 
verted into hydroxide. 

BaO 4- H^'O = Ba(0H)2 

Barium oxide. Barium hydroxide. 

In the same manner, the oxides of potassium and sodium 
energetically absorb the elements of water, being converted 
into hydroxides. 

K^O + H^O = 2K0H 

Potassium oxide. Potassium hydroxide. 

The hydroxides of potassium and sodium are soluble in 
water, and their solutions are caustic, changing tincture of 
violet to a green color and restoring the blue color to reddened 
litmus solution. These hydroxides constitute the alkalies. 

The hydroxides of barium, strontium, and calcium are like- 
wise soluble in water to a certain extent, and their solutions 
are also somewhat caustic. 

Other hydroxides are insoluble ; they may be obtained by 
double decomposition by precipitating the corresponding salts 
with an alkali. 

If a solution of potassium hydroxide be poured into a solu- 
tion of cupric sulphate, a light-blue precipitate of cupric 
hydroxide is formed. 

CuSO^ + 2K0H = K^SO* + Cu(OH)^ 

Cupric sulphate. Potassium hydroxide. Potassium sulphate. Cupric hydroxide. 

But if this precipitate be heated, even in the liquid in 
which it was formed, it changes to brown, and is converted into 
oxide by losing its water. 

Cu(OH)^ — H^O -- CuO 



SULPHIDES. 257 

A great number of metallic hydroxides undergo the same 
decomposition when they are heated. 

There are true metallic acids which contain the elements of 
an oxide plus the elements of water. Such are 

H^CrO' = CrO' + H^O 

Chromic acid. Chromium trioxide. 

H^MnO* = MnO^ + H=^0 

Maogauic acid. Manganese trioxide. 

As far as their constitution is concerned, these metallic acids 
may be compared to sulphuric acid. 

H^SO^ = 80=^ -I- WO 

They also resemble sulphuric acid in their chemical func- 
tions ; each contains two atoms of basic hydrogen, that is, two 
atoms of hydrogen which are replaceable by a metal. 



SULPHIDES. 

Sulphur has a great tendency to unite with the metals, and 
the union often takes place with a vivid evolution of heat. 
Copper-turnings and iron-filings burn in the vapor of sulphur. 
The phenomena which favor or determine, and those which 
accompany this combination, have already been indicated, and 
we have seen that the presence of a small quantity of water 
favors chemical union in a mixture of sulphur and iron-filings. 

In composition the sulphides are analogous to the oxides. 

The more important of the transformations which they may 
undergo are the following: 

Oxygen decomposes all of the sulphides at a temperature 
more or less elevated. 

Finely-divided potassium sulphide, obtained by calcining the 
sulphate with an excess of charcoal, is a black powder, but it 
becomes incandescent on contact with oxygen, and if thrown 
into the air it produces a shower of sparks. It is known as 
Gay-Lussac's pyrophorus. Its fine state of division favors the 
absorption of oxygen, and the latter converts it into sulphate. 
K^S 4- 0* = K^SO^ 

Potassium sulphide. Potassium sulphate. 

Dry oxygen acts in the same manner upon all the sulphides 
when the corresponding sulphates are stable at high tempera- 
tures. In the contrary case, sulphur dioxide is formed, and 
r 22* 



258 ELEMENTS OF MODERN CHEMISTRY. 

a residue of oxide or even of metal is obtained, if the oxide be 
decomposable by heat. 

If zinc sulphide be roasted, it is converted into zinc oxide, 
and sulphur dioxide is evolved; but if sulphide of mercury- 
be heated in a current of air, metallic mercury is obtained. 

HgS + 0^ = Hg + SO^ 

Mercuric sulphide. Mercury. 

Moist oxygen acts upon the sulphides more readily than the 
dry gas. It unites with them at ordinary temperatures, form- 
ing sulphates. 

FeS 4- 0* = FeSO* 

Sulphide of iron. Ferrous sulphate. 

Chlorine attacks all of the sulphides, forming metallic chlo- 
rides and sulphur chloride, if the dry method be employed, or 
with deposition of sulphur if the reaction take place in presence 
of water. 

Water dissolves the alkaline sulphides as well as those of cal- 
cium, barium, and strontium ; the sulphides of the other metals 
are insoluble in water. 

Hydrogen sulphide combines with certain sulphides, convert- 
ing them into hydrosulphides. The analogy will be noticed 
between this reaction and that of water upon the oxides. 

K^S + ffS = 2KSH 

Potassium sulphide. Potassium hydrosulphlde. 

K^O -h H^O = 2K0H 

Potassium oxide. Potassium hydroxide. 

CHLORIDES. 

Chlorine, bromine, and iodine form with the metals com- 
pounds which possess the appearance and certain properties of 
salts. Indeed, common salt, or sodium chloride, has given the 
name to the entire class of saline compounds. Hence Berze- 
lius named chlorine, bromine, and iodine the halogen bodies, 
and called their combinations with the metals the haloid salts. 
Thus he admitted the relation between these compounds and 
the true salts, while at the same time distinguishing them by a 
particular name, for while they resemble the salts in their prop- 
erties, they differ from them in composition. This subject will 
be more fully considered farther on. 

Composition. — The metals, as a rule, combine directly 
with chlorine, but the different metals do not combine with 



CHLORIDES. 



259 



it in the same atomic proportions, and often the same metal 
forms several distinct combinations with this element. Hence 
the differences in the composition of the chlorides. They are 
formed by the union of an atom of metal with one, two, three, 
four, five, or six atoms of chlorine. 



KCl 


CaCP 


SbCP 


SnCP 


SbCP 


MoCP 


Potassium 
chloride. 


Calcium 
chloride. 


Antimony 
trichloride. 


Tin 
tetrachloride. 


Antimony 
pentachloride. 


Molybdenum 
hexachloride. 


NaCl 


FeCP 


BiCP 


TiCP 


WCP 


WCP 


Sodium 
chloride. 


Ferrous 
chloride. 


Bismuth 
trichloride. 


Titanium 
tetrachloride. 


Tungsten 
pentachloride. 


Tungsten 
hexachloride. 


AgCl 


ZnCP 


AuCP 


PtCP 






Silver 
chloride. 


Zinc 
chloride. 


Gold 
trichloride. 


Platinum 
tetrachloride. 






CuCl 


CuCP 


AlCP 








Cuprous 
chloride. 


Cupric 
chloride. 


Aluminium 
chloride. 








HgCl 

Mercurous 
chloride. 


HgCP 

Mercuric 
chloride. 


CrCP 

Chromic 
chloride. 









It is seen that the same metal may form several combina- 
tions with chlorine. 

Mercury and copper combine with one or two atoms of chlorine. 
Iron combines with two or three atoms of chlorine. 
Tin and platinum combine with two or four atoms of chlorine. 
Tungsten combines with four, five, or six atoms of chlorine. 

Owing partly to faulty determinations, and partly to anom- 
alies in their vapor densities, some of the chlorides of the 
first and the third of the above series were for a long time 
regarded as consisting of two atoms of metal combined with 
two and with six atoms respectively of chlorine. Thus mer- 
curous chloride was represented by the formula Hg^CP, and 
that of aluminium chloride was written APCP. In these, as 
well as in analogous cases, it has been shown that the vapor 
densities and other physical constants, when determined under 
the proper conditions, accord perfectly with the simpler for- 
mulae given above. 

Physical Properties of the Chlorides. — Most of the chlo- 
rides are solid and possess the aspect, color, and physical prop- 
erties of the salts of the same metal. Nearly all are crystalline 
and soluble in water. Only the chloride of silver, mercurous 



260 ELEMENTS OP MODERN CHEMISTRY. 

and cuprous chlorides are insoluble ; lead chloride and thal- 
lous chloride are but slightly soluble in water. 

Certain metallic chlorides are liquid at ordinary tempera- 
tures. Such are the tetrachlorides of tin and titanium. Some, 
like the chlorides of zinc and bismuth, are solid, but fusible at 
low temperatures. These latter were formerly designated as 
metallic butters. 

Most of the chlorides are fusible at high temperatures, and 
many of them are volatile and can be distilled without altera- 
tion. It is thus with the liquid chlorides, with the chlorides 
of zinc, bismuth, mercury, etc. 

Chemical Properties. — As a rule, the chlorides are very 
stable. Only the chlorides of certain of the precious metals, 
as those of gold and platinum, are entirely decomposed by a 
high temperature. Some of the higher chlorides lose chlorine 
when calcined, and are converted into lower chlorides. Thus, 
cupric chloride is converted into cuprous chloride when heated 
out of contact with. air. 

A great number of the chlorides are reduced when they are 
heated in a current of hydrogen. In this case, hydrochloric 
acid is disengaged, and the metal remains. Thus, hydrogen 
removes the chlorine from the chlorides of silver and iron. 
These decompositions are determined by the powerful affinity 
of chlorine for hydrogen. 

The action of the metals upon the chlorides gives rise to 
interesting phenomena which are worthy of study. 

If corrosive sublimate, which is mercuric chloride, be mixed 
with powdered tin and the mixture be heated in a small glass 
retort provided with a receiver, a liquid will soon collect in the 
latter which diffuses thick vapors in the air. It is the tetra- 
chloride of tin, which was formerly known as " fuming liquor 
of Libavius." It is formed by the decomposition of the mer- 
curic chloride, which gives its chlorine to the tin, metallic 
mercury being at the same time set free. 

Bismuth decomposes mercuric chloride in the same manner 
when the two substances are heated together. These experi- 
ments are conducted in the dry way. They may be modified 
by operating in the presence of water, in which we have re- 
marked that most of the chlorides are soluble ; it is thus with 
mercuric chloride. 

If a plate of copper be plunged into a solution of this body, 
it at once becomes covered with a layer of metallic mercury. 



CHLORIDES. 261 

That metal is displaced from its combination by the copper, 
wbicb combines with tbe chlorine : cupric chloride is formed, 
and after the lapse of some time, the liquid will contain only 
that compound. It becomes green, and if a plate of zinc be 
plunged into it, the copper will be precipitated in its turn, and 
the zinc will combine with the chlorine and enter the solution ; 
the liquid then contains zinc chloride. 

Thus, the metals mutually displace each other from their 
solutions, according to the energy of their affinities. In this 
case it is the possession of the chlorine for which they antago- 
nize each other, the stronger driving out the weaker. It must 
be remarked that in this respect the chlorides behave in the 
same manner as the oxygen salts. 

This analogy is continued in innumerable reactions. Solu- 
tions of the chlorides enter into double decompositions like 
solutions of the true salts. If potassium hydroxide be added 
to a solution of either cupric sulphate or cupric chloride, in each 
case a light-blue precipitate of cupric hydroxide is obtained. 

CuSO* + 2K0H = K^SO* + Cu(OH)*^ 

Cupric sulphate. Potassium liydroxide. Potassium sulphate. Cupric hydroxide. 

CuCP + 2K0H = 2KC1 + Cu(0H)2 

Cupric chloride. Potassium chloride. 

But cupric chloride resembles the sulphate in still another 
property. When perfectly pure it is yellowish. If it be moist- 
ened with water, it becomes heated and assumes a green color. 
It has combined with water, and will dissolve if enough of that 
liquid be added. A green liquor is thus obtained, which de- 
posits, by spontaneous evaporation, magnificent green prisms. 
These crystals are hydrated cupric chloride. They contain 
water of crystallization, and can only exist on that condition. 
It is the same with the crystals of cupric sulphate. 

Thus, certain chlorides are capable of taking water of crys- 
tallization like the true salts. 

We may complete the analogy by one more characteristic. 

1. If a solution of aluminium sulphate be added to a con- 
centrated solution of potassium sulphate, and the mixture be 
agitated, an abundant crystalline deposit is obtained. This is 
a double salt, — potassium and aluminium sulphate, or alum. 

2. If a solution of platinic chloride be added to a concen- 
trated solution of potassium chloride, a yellow precipitate is 



262 ELEMENTS OF MODERN CHEMISTRY. 

formed at once. It is the double chloride of potassium and 
platinum, which contains all of the elements of two molecules 
of potassium chloride and one molecule of platinic chloride. 
This example shows that the chlorides can combine together, 
forming double chlorides, just as the true salts may combine 
together to form double salts. 



SALTS. 

Definition. — The salts are formed by the substitution of 
metal for the hydrogen of the acids, and they result from the 
action of the acids upon the metallic oxides or hydroxides. The 
name acid applies to two classes of compounds : the first are 
formed by the union of hydrogen with a strongly electro-nega- 
tive element, such as chlorine or bromine ; these are the hy- 
dr acids. Such are hydrochloric acid, HCl, and hydrobromic 
acid, HBr. 

The acids of the other class are more complicated, contain- 
ing hydrogen united with a strongly electro-negative oxidized 
group, that is, a group of atoms formed by oxygen and another 
element ; these are the oxyacids. Such are nitric acid^ HNO^, 
and sulphuric acid, H^SO*. 

These two classes of acids behave in the same manner in 
contact with basep, that is, with metallic oxides or hydroxides. 

1. If hydrochloric acid be gradually added to a concentrated 
solution of potassium hydroxide, the liquid becomes heated, 
and, as it is neutralized by the acid, a white crystalline de- 
posit separates and augments on cooling : it is potassium 
chloride. 

2. If sulphuric acid diluted with its volume of water be 
cautiously and gradually added to a concentrated solution of 
potassium hydroxide, the liquid becomes heated, and, as it is 
neutralized by the acid, a white crystalline deposit separates 
and increases on cooling : it is potassium sulphate. 

The analogy between the two reactions is marked. In each 
case a powerful base, potassium hydrate, has been neutralized 
by an energetic acid; the reaction has been accompanied by 
the production of heat, and has given rise to the formation 
of a saline matter which has been deposited. The part of the 
reaction which is invisible is the formation of water. This 
formation of waterj which always accompanies the generation 



SALTS. 263 

of a salt in the ordinary manner, is expressed in the following 

equations : . ' 

KOH -f HCl = KCl + WO 

Potassium hydroxide. Potassium chloride. 

2K0H + H^SO* = K^SO* + 2H^0 

Potassium sulphate. 

These reactions, it will be seen, consist in an interchange of 
elements, a double decomposition. The hydrogen of the acid 
is exchanged for the metal of the potassium hydroxide and by 
the exchange the potassium hydroxide is converted into water, 
while the acid, that is, the salt of hydrogen, is converted into a 
salt of potassium. All hydrogen compounds capable of thus 
exchanging their hydrogen for an equivalent quantity of metal, 
fill the functions of acids, and these acids become salts when 
their hydrogen is thus replaced by a metal. It may then be 
seen what an important part hydrogen plays in the formation 
of salts. Whence comes this property, this capacity for making 
such exchanges, and for replacement by metals? Without 
doubt from the element or group with which the hydrogen is 
united in the acids ; and in this respect chlorine and sulphur 
play the same parts in hydrochloric and hydrosulphuric acid's 
that the oxidized groups play in nitric, sulphuric, and phos- 
phoric acids. 

HCl H^S 

Hydrochloric acid. Sulphydric acid. 

H(NO^) H^CSO^) H^^CPO^ 

Nitric acid. Sulphurous acid. Phosphorous acid. 

H(CIO^) H\SO*) H\PO*) 

Chloric acid. Sulphuric acid. Phosphoric acid. 

This property is characterized by saying that the elements or 
groups, to which the hydrogen is united, are strongly electro- 
negative, or acid, in opposition to the hydrogen, which is 
strongly electro-positive, or basic. 

When such an acid reacts upon an oxide, or upon a hydroxide, 
an interchange of elements takes place, and a salt and water 
are formed ; the latter is a constant product necessary to the 
reaction. Other examples may be added to those already given. 

If a current of hydrogen sulphide be passed into a solution 
of potassium hydroxide until no more is absorbed, potassium 
hydrosulphide and water are formed, 

ffS -f KOH = KSH + H^O 

Potassium hydrosulphide. 



264 ELEMENTS OF MODERN CHEMISTRY. 

If an excess of dilute sulphuric acid be poured into a solu- 
tion of potassium hydroxide, potassium acid sulphate and water 
are formed. 

ff SO* + KOH = KHSO* + ff 

Potassium acid sulphate. 

Lastly, if cupric oxide be heated with dilute sulphuric acid, 
it dissolves, coloring the liquid blue. Cupric sulphate and 
water are formed. 

H^SO* _|_ CuO = CuSO* + H^O 

Cupric oxide. Cupric sulphate. 

Neutral, Acid, and Basic Salts. — If the salts result from 
the substitution of the metals for the basic hydrogen of acids, 
it is evident that their composition must be related to that of 
the acids from which they are derived. We know that the 
latter contain one, two, or three atoms of hydrogen, capable of 
being replaced by an equivalent quantity of metal : they are 
monobasic, dibasic, and tribasic. It is evident that the salts 
must present analogous differences in their composition, accord- 
ing as they are derived from a monobasic, a dibasic, or a tribasic 
acid. 

A salt is neutral when the basic hydrogen has been entirely 
replaced by an equivalent quantity of metal. But the substi- 
tution may be only partial, for when an acid contains two atoms 
of basic hydrogen, only one of these atoms may be replaced by 
one atom of metal ; there will then remain in the salt thus 
formed one atom of basic hydrogen. 

When an acid contains three atoms of basic hydrogen, it 
may happen that only one is replaced by one atom of metal ; 
there will then remain in the salt two atoms of basic hydrogen ; 
or it may be that two atoms of hydrogen are replaced by an 
equivalent quantity of metal, and there will then remain in the 
salt a single atom of basic hydrogen. 

Whenever basic hydrogen thus remains in a salt, the satura- 
tion of the acid is said to be incomplete. The salt formed 
ordinarily retains the characters of an acid ; it is an acid salt. 
The following table indicates the possible cases of complete 
or incomplete saturation which may be presented by a mono- 
basic, a dibasic, and a tribasic acid : 

HNO^ H^SO* HTO* 

J^itric acid. Sulphuric acid. Phosphoric acid. 



SALTS. 265 

KNO^ || SO* ^2 [ PO* 

Potassium nitrate. Potassium acid sulphate. Monopotassium phosphate. 

K^SO* g I PO* 

Potassium sulphate. Dipotassium phosphate. 

Tripotasslum phosphate. 

Certain neutral salts possess the property of combining with 
the hydroxides or the oxides. The compounds so formed con- 
tain all the elements of the neutral salt plus those of the 
hydroxide or oxide ; they are called basic salts. Thus, the oxides 
of lead and copper may combine with the various salts of lead 
and copper, forming basic salts of those metals. 

Richter's Laws. — Towards the close of the last century 
fruitful investigation was made into the phenomena of neu- 
tralization or saturation of acids by bases. We know that a 
given weight of acid requires for its neutralization a fixed and 
absolutely invariable quantity of a given base. Thus, for the 
conversion of 1000 grammes of sulphuric acid into neutral 
potassium salt, a quantity of potassium hydrate corresponding 
to 961 grammes of potassium oxide, K^O, is required. To 
saturate these 1000 grammes of sulphuric acid, it is necessary 
to take weights of the oxides which are invariable for each one 
separately, but which vary among themselves. 

Thus, 1000 grammes of concentrated sulphuric acid are neu- 
tralized by the following quantities of the oxides named : 

Potassium oxide 961 grammes. 

Sodium oxide 632 " 

Barium oxide 1561 " 

Calcium oxide 571 " 

Zinc oxide 866 " 

Cupric oxide 811 " 

Mercuric oxide 2204 " 

Silver oxide 2367 " 

Again, to neutralize 1000 grammes of the most concentrated 
nitric acid, the following quantities of the same oxides are 
required : 

Potassium oxide 747 grammes. 

Sodium oxide 492 " 

Barium oxide 1214 " 

Calcium oxide 444 " 

Zinc oxide 651 " 

Cupric oxide 631 « 

Mercuric oxide 1714 "' 

Silver oxide 1841 ** 

M 23 



266 ELEMENTS OF MODERN CHEMISTRY. 

Ricliter was the first to remark that these latter quantities 
are precisely in the same ratio to each other as the quantities 
of oxides which neutralize 1000 grammes of sulphuric acid. 
Thus, 

961 ^ 747 

632 492 

961 _ 747 

1561 ~1214 

'J} =lfL, etc. 
571 444 

In other words, the quantities of oxides which neutralize a 
given weight of one acid are proportional to the quantities of 
the same oxides which neutralize the same weight of another 
acid. This law of the composition of salts was discovered, 
towards the close of the last century, by Kichter, a chemist of 
Berlin. It is the law of relative combining proportions, applied 
to particular cases and the reactions of compounds, but soon 
afterwards to be generalized by Daiton and expressed as the 
fundamental law of chemical combination. 

Richter also studied the phenomenon of the precipitation of 
metallic solutions by the metals. It is known that when a 
piece of iron is plunged into a solution of cupric sulphate, the 
iron dissolves, displacing a certain quantity of copper, without 
other change. Since the new salt formed, ferrous sulphate, ex- 
ists in the solution in the same conditions of neutrality as the 
cupric sulphate, the quantities of metal which thus displace 
each other are equivalent. As neither oxygen nor acid is set 
at liberty, it must be admitted that the respective quantities of 
the metals, in the salts successively formed, are united to the 
same quantity of oxygen. It has even been supposed that in 
the salts which, like the sulphates, contain four atoms of oxygen, 
the metal is in intimate relation with one of these atoms, which 
is precisely sufficient to constitute the metal in the state of 
monoxide. 

CuSO* = CuO,SO^ 
FeSO* = FeO,SO' 

If this were so, it is evident that when cupric sulphate is 
decomposed by iron, the quantity of metal which enters into 
solution would combine or enter into relations with precisely the 
quantity of oxygen abandoned by the copper. This quantity of 
oxygen being constant, the quantities of the metals which com- 



SALTS. 267 

bine successively with it, differ, but are equivalent to each 
other, and it is evident that the oxides thus formed would be 
more rich in oxygen as the weight of metal which enters into 
solution is less considerable; in other words, the richness of all 
these oxides in oxygen is inversely proportional to the weights 
of the metals which successively become dissolved ; it was in 
this form that Kichter announced the second law of the com- 
position of salts. It will be seen that this law is implied in 
the first, and that both are but particular cases and natural con- 
sequences of the theory of equivalents, as it is understood at 
present and as it has already been explained (page 33). 

General Properties of Salts. — The salts present very differ- 
ent colors. Those which are formed by an acid possessing a 
color are themselves colored ; such are the chromates, manga- 
nates, and permanganates. 

Most of the colored oxides form salts presenting various 
colors. 

Ferrous salts are bluish-green. 

Ferric salts are yellow or yellowish-brown. 

Manganese salts are pink. 

Chromium salts are dark green or red. 

Nickel salts are green. 

Cobalt salts are currant-red. or blue. 

Cupric salts are blue or green. 

Gold salts are yellow. 

It is to be remarked that these various colors are only devel- 
oped, as a rule, when the salts are hydrated, that is, combined 
with water of crystallization. The taste of the salts depends 
upon their solubility ; it is wanting altogether or but slightly 
marked in the insoluble salts ; more or less pronounced and 
very diverse in the soluble salts. The salts of magnesium are 
bitter ; the aluminium salts are astringent ; those of iron astrin- 
gent, with a metallic after-taste; the salts of lead are at the 
same time sweet and astringent ; the salts of copper, antimony, 
and mercury have an acrid metallic taste, which is nauseous, 
and is called styptic. 

The salts generally occur in crystalline form. Some of them 
may be obtained as amorphous precipitates, but if such salts 
be formed slowly under circumstances favoring crystallization, 
they also assume the form of crystals. 

Isomorphism. — Certain salts which possess similar atomic 
compositions crystallize in identical or nearly identical forms; 
they are called isomorphous. It is thus with the double sul- 



268 ELEMENTS OF MODERN CHEMISTRY. 

phates, wHich are called alums, and of whicli ordinary alum 
or aluminium and potassium sulphate is the type. These alums 
are formed by the union of a sulphate, R^SO*)^, with a sul- 
phate, M^SO*, and they all contain 24 molecules of water of 
crystallization. 

Thus, ordinary alum, 

AP(SO^)lK=^SO' + 24H^O 

Aluminium and potassium double sulphate. 

is isomorphous with chrome alum and iron alum. 
Cr^(SO^)lK^SO* + 24ffO 

Chromium and potassium double sulphate. 

Fe\SO*)lK^SO* + 24H20 

Iron and potassium double sulphate. 

All of these alums crystallize in regular octahedra. Further, 
a solution containing two alums, for example, aluminium and 
potassium sulphate and aluminium and ammonium sulphate, 
deposits on concentration crystals in which the two salts are 
mixed. Such is the character of isomorphous bodies ; crystal- 
lizing in the same form, they may mix together and replace 
each other in all proportions in the same crystal. Many exam- 
ples of isomorphism will be cited in the course of this work. 
It will now be sufficient to add that this idea of isomorphism 
has rendered valuable service to chemical theory by permitting 
the grouping together of bodies similar both in crystalline form 
and atomic constitution, and by furnishing in such cases useful 
indications for the determination of the atomic weights. It is 
evident that when two similar combinations, two sulphates, for 
example, are recognized to be isomorphous, it is necessary to 
represent their constitutions by analogous formulae, and the 
latter can only be possible under the condition that the atomic 
weights of the metals contained in these sulphates have known 
values. 

Action of Water upon the Salts. — If water be poured upon 
and agitated with powdered chalk, a white, cloudy liquid is 
obtained. The chalk is suspended in the water without being 
dissolved ; it is simply held up in the form of minute particles, 
and if the liquid be allowed to stand, the precipitate is de- 
posited, and clear water again appears above the deposit. 

However, if saltpetre, or potassium nitrate, be agitated with 
water, a colorless, transparent liquid is obtained. The saltpetre 
is dissolved in the water; it has disappeared as a solid body. 



SALTS. 269 

It is melted by tlie water, as is commonly said, and is uniformly 
diffused through the liquid. It has itself become liquid, and 
this is the phenomenon of solution. It is accompanied by a 
production of cold, that is, an absorption of heat ; for in assum- 
ing the liquid state and becoming diffused throughout the water, 
the saltpetre must absorb heat. 

If the introduction of powdered nitre into the solution m 
continued, the solid still disappears, but a time arrives when\ 
the salt introduced ceases to dissolve ; for water at a given tem- 
perature can only dissolve a fixed quantity of a salt, and when 
this limit is attained, the solvent force of the water upon the salt- 
petre is exhausted. The water is then said to be saturated with 
the salt, and any excess of the latter remains in the solid state. 

But if now the solution be heated, this excess is in its turn 
dissolved, for the solubility augments with the temperature, 
and as the latter is raised, a larger quantity of the salt is dis- 
solved. When the liquid begins to boil, the temperature and 
the solubility of the salt have reached their extreme limit. 

If the boiling saturated solution be allowed to cool, it depos- 
its a large portion of the salt in the form of crystals. In this 
manner voluminous, colorless, and transparent prisms are ob- 
tained which fill the vessel, and which are surrounded by a 
solution of saltpetre, saturated at the temperature to which the 
liquid has been cooled. This liquid is called the mother-liquor 
of the crystals. It is thus that soluble salts are crystallized by 
cooling their hot saturated solutions. 

G-enerally the same facts are observed for other soluble salts. 
Their solubility increases with the temperature; there are, 
however, some exceptions to this rule. Sodium chloride is 
but slightly more soluble in hot than in cold water, and gypsum, 
or calcium sulphate, is sensibly more soluble in cold than in hot 
water; for, while 500 parts of boiling water are requisite to 
dissolve one part of gypsum, only 460 parts of cold water are 
necessary to dissolve the same quantity. The maximum solu- 
bility of sodium sulphate is between 32 and 33°. 

Crystals of nitre may be obtained by another process. We 
may expose the cold saturated solution to the air at the ordi- 
nary temperature, or, better still, place it in a bell-jar over a 
vessel containing sulphuric acid. The water of the solution 
slowly disappears, and, as it is dissipated in vapor, a portion of 
the dissolved salt separates in the solid form. The crystals thus 
formed by spontaneous evaporation are generally very regular. 

23* 



270 ELEMENTS OP MODERN CHEMISTRY. 

But water exerts another and a different action upon the 
sahs. 

Perfectly dry cupric sulphate, CuSO*, is a white powder. 
If water be poured upon it, it becomes blue and dissolves, com- 
municating to the liquid a blue color and notably raising its 
temperature. On evaporation, this liquid deposits crystals of 
blue vitriol, and if these be compared with the dry white pow- 
der with which we started, they will be found to differ from it 
by the water they contain. We have employed the anhydrous 
salt, and have hydrated it. In fact, the sulphate, CuSO*, has 
absorbed five molecules of water, with which it has combined, 
and this combination, like all others, has taken place with the 
production of heat. The water which is thus absorbed by cer- 
tain salts, and which combines with them in definite propor- 
tions, is necessary to the formation of their crystals ; it is called 
water of crystallization. 

It is not necessary to the constitution of the salts them- 
selves ; they can exist without it, and generally lose it when 
they are heated to a temperature more or less elevated, without 
undergoing any other decomposition. Certain salts abandon 
their water of crystallization with such facility that they give 
it up to the surrounding air when the latter is not saturated 
with moisture. They then become opaque and lose their 
forms, for crystals cease to exist when their water of crystalli- 
zation is disengaged. These salts become covered with a dry 
powder in the air and are called efflorescent salts. 

It is seen by the example just cited that the phenomenon 
of solution of salts in water, which depends upon a physical 
action, upon a change of state, is often complicated with a true 
combination of the salt with water, that is, a chemical action 
which disengages heat. The latter is generally more energetic 
than the physical action, and the difference between the two 
effects is then manifested by an elevation of temperature. 

But the physical phenomenon is produced alone when the 
salt which dissolves is incapable of combining with water of 
crystallization. A depression of temperature is then observed, 
as we have seen in the case of nitre, the crystals of which are 
anhydrous; but another example will more clearly illustrate 
this important phenomenon. 

If water be poured upon recently fused and powdered calcium 
chloride, the salt dissolves with production of heat. It changes 
not only its state but its composition ; it combines energetically 



SALTS. 271 

with the water, and this combination produces more heat than 
is absorbed by the change of state. Hence there is an eleva- 
tion of temperature. 

If calcium chloride, combined with its water of crystalliza- 
tion, be rapidly mixed with snow, the salt is so soluble in water 
that it causes the snow to melt at the same time that it becomes 
liquid itself Here there is no combination, no chemical action, 
and no heat is disengaged. It is a double physical phenome- 
non, — fusion of the snow and fusion of the calcium chloride, — 
and neither of these bodies can undergo a change of state with- 
out absorbing heat. Hence there is a depression of tempera- 
ture which may reach — 40°. 

A mixture of snow and calcium chloride is a freezing mix- 
ture. A mixture of equal parts of common salt and broken 
ice or snow is frequently used for the production of cold. 

The phenomenon of the solution of salts in water presents 
none of the characteristics of a chemical action; it does not 
take place in definite proportions. 

In fact, a soluble salt requires for its complete solution a 
quantity of water, which is always the same for a certain weight 
of the salt at a given temperature ; but there exists no atomic 
relation between this quantity of water and the weight of the 
salt which is dissolved. 

Further, although the solubility of a salt presents for each 
temperature a maximum limit, that is, although a given weight 
of a salt requires for its solution a quantity of water which is 
invariable and which cannot be diminished, when the solution 
has been accomplished an indefinite quantity of water may be 
added, and the liquid will still remain perfectly homogeneous. 

Super saturation. — We have seen that a saturated solution 
of a salt at a given temperature generally deposits a part of 
that salt on cooling. This is not always the case ; it sometimes 
happens, if the cooling take place under certain conditions, that 
a portion of the salt, which the difference in temperature should 
reduce to the solid state, still remains in solution. The solu- 
tion is then said to be supersaturated. Sodium sulphate and 
alum have a great tendency to form such solutions. 

A hot, saturated solution of sodium sulphate is contained in 
the tube A (Fig. 95). It is heated to boiling, so that the vapor 
escapes by the drawn-out extremity. By the aid of a blow- 
pipe, the tube is then sealed at C, before the vapor can con- 
dense, and is then allowed to cool. A vacuum is formed above 



272 



ELEMENTS OF MODERN CHEMISTRY. 



the solution, for the air has been driven out by the vapor. The 
cold liquid remains limpid ; it deposits no crystals. But the 
instant the drawn-out point of the tube is broken off, the air 
enters and crystallization at once commences at the surface and 




Fig. 95. 

proceeds throughout the entire mass, which becomes solid ; at 
the same time an elevation of temperature may be observed. 

100 grammes of water and 200 grammes of crystallized so- 
dium sulphate may be heated to ebullition in a narrow-necked 
flask, and as soon as vapor begins to issue from the mouth, the 
latter may be covered with a watch-glass and the whole allowed 
to cool tranquilly. The salt remains dissolved, and the solution 
contained in the flask is supersaturated; but as soon as the 
watch-glass is removed the liquid becomes a solid mass of crys- 
tals (Loewel). 

In the first experiment it is the sudden entry of the air 
which determines the crystallization; in the second, it is the 
free access of air, and it may be admitted that in each case the 
air acts by the corpuscles which it holds in suspension, and 
which, falling into the solution, determine the crystallization. 
Indeed, Loewel has shown that air which has been filtered 



SALTS. 273 

through cotton-wool has lost the property of causing supersat- 
urated solutions to crystallize. 

But what is the nature of these particles which by falling 
upon the surface of supersaturated solutions occasion crystalli- 
zation ? The researches of Gernez have thrown great light upon 
this question. According to him, they are saline particles simi- 
lar to the salt dissolved. The sodium sulphate is deposited in 
the preceding experiments because the entry of the air has 
allowed an imperceptible particle of sodium sulphate to fall 
upon the surface of the liquid, and around this particle the 
crystallization begins immediately and is propagated through- 
out the entire mass of the supersaturated liquid. The air then 
contains a trace of sodium sulphate, as it contains a trace of 
common salt and of carbonate and sulphate of calcium. These 
particles are suspended in the air in a state of extreme division, 
and are carried from great distances by the winds. 

A boiling saturated solution of sodium hyposulphite may be 
allowed to cool in a carefully-corked flask. When cold, it is so 
concentrated that it possesses an oily consistency. The flask 
may be carefully uncorked and the surface of the liquid touched 
with a rod to the end of which a small particle of sodium hy- 
posulphite has been made to adhere. Crystallization at once 
commences at the spot where the rod touches the liquid, and 
in a few seconds the whole mass becomes solid. There is at 
the same time a notable disengagement of heat (Grernez). 

The crystallization will also take place if a particle of sodium 
sulphate be allowed to fall into the solution, for the latter salt 
possesses the same crystalline form as sodium hyposulphite, and 
an analogous constitution. 

Ebullition of Saline Solutions. — Aqueous solutions of the 
salts generally possess a boiling-point higher than that of water. 
Thus, a saturated solution of common salt boils at 108.4° ; a 
saturated solution of potassium nitrate boils at 115.9°; and a 
saturated solution of calcium chloride boils only at 179.5°. 

Action of Heat upon the Salts. — The hydrated salts lose 
their water when they are heated. Ordinarily, a temperature 
of 100° is sufficient to expel the water of crystallization. Cer- 
tain salts melt in this water before losing it ; they are so soluble 
in hot water that they dissolve in the water which at a lower tem- 
perature constitutes them in the crystalline state. This is called 
aqueous fusion. A great number of anhydrous salts melt when 
they are exposed to intense heat ; this is called igneous fusion. 



274 



ELEMENTS OF MODERN CHEMISTRY. 



Heat exerts a decomposing action upon many salts. Upon 
this point it is difficult to give general laws. It can only be 
said that the stability of a salt depends upon three conditions, 
namely, the fixedness of the corresponding acid, the stability 
of the corresponding oxide, and the energy of the affinity with 
which the two react together to form the salt. 

Thus the salts of acids decomposable by heat are themselves 
decomposed at an elevated temperature. It is thus with the 
chlorates, the perchlorates, and the nitrates. Among the sul- 
phates, some are decomposable, others are fixed. The latter are 
those of potassium, sodium, barium, strontium, calcium, mag- 
nesium, lead, etc. The corresponding oxides of potassium, 
sodium, barium, etc., are fixed bases, and possess a powerful 
affinity for sulphuric acid. Hence their sulphates are stable. 

Most of the carbonates are decomposable by heat; indeed, 

the affinity of carbonic acid for the bases is as a rule feeble. 

It is exceptionally strong for the alkaline bases ; hence the 

alkaline carbonates resist the action of heat. 

Action of Electricity upon the Salts. — When an electric 

current traverses the aque- 
ous solution of a salt, the 
latter is decomposed. The 
metal separates at the neg- 
ative pole, and the other 
element of the salt at the 
positive pole. This other 
element may be an elec- 
tro-negative element, such 
as chlorine, or an oxidized 
group, that is, a group of 
atoms, one or more of 
which is oxygen. 

The electrolysis of a 

salt may be eff'ected as 

follows: An U tube (Fig. 

96) contains a solution of 

cupric chloride. In each 

branch a plate of platinum 

dips into the liquid, and 

Fig. 96. these plates, connected by 

conducting wires with the two poles of a battery, constitute 

the positive and negative electrodes 




As soon as the current 



SALTS. 275 

passes, the electro-positive element of tlie salt, the copper, is 
deposited upon the electro-negative electrode, and the chlorine, 
which, is electro-negative, is disengaged at the positive electrode. 
A part of this chlorine combines with the platinum electrode 
by a secondary reaction, forming platinum chloride, but the 
principal action, that is, the decomposition of cupric chloride 
by electrolysis, is represented by the following equation: 

CuCP = Cu -f ci^ 

Cupric chloride. Copper. Chlorine. 

If the cupric chloride be replaced by cupric sulphate, the 
current will decompose this salt into copper, which deposits 
upon the negative electrode, and into SO*, which possesses no 
stability, and consequently breaks up at the positive electrode 
into SO^, which combines with the water to form sulphuric 
acid, and 0, which is disengaged at the positive electrode. 

The decomposition of the SO* is a secondary action. The 
principal action accomplished by the work of the current is 
expressed by the following equation : 

CuSO* = Cu + SO* 

Cupric sulphate. Copper. Oxidized group. 

The secondary reactions are as follows : 
SO* == SO^ + 
SO^ -f H^O = H^SO* 

The experiment may be repeated upon potassium sulphate, 
and a solution of this salt colored by the syrup of violets is in- 
troduced in the U tube. As soon as the current passes, bub- 
bles of gas are seen to arise from each electrode. Free oxygen 
appears at the positive electrode, as in the preceding case, and 
at the same time the liquid filling this branch of the tube as- 
sumes a red color. This is the evidence of the presence of 
sulphuric acid formed at the positive electrode. 

The gas disengaged at the negative electrode is hydrogen, 
which is produced by a secondary action of the water upon the 
potassium which is removed from the salt at the negative pole. 
Potassium hydroxide is thus formed, and the syrup of violets 
in this branch of the tube is colored green. The principal ac- 
tion accomplished by the current is expressed, as in the pre- 
ceding cases, by the equation 

K'SO* = 2K + SO* 

Potassium sulphate. Potassium. Oxidized group. 



276 ELEMENTS OP MODERN CHEMISTRY. 

The appearance of hydrogen and potassium hydroxide at 
one pole, and the disengagement of oxygen and formation of 
sulphuric acid at the other, are due to secondary reactions inde- 
pendent of the current, as has been explained. 

The positive pole is called the anode, and the negative pole 
the cathode, and the elements or groups which separate are 
distinguished as anions and cathions, according to the poles at 
which they are set free. The groups into which a compound 
is separated by the electric current are called the ions. 

According to a theory proposed by Arrhenius, a salt in dilute 
solution exists as such only in small proportion, the larger pro- 
portion being dissociated into the ions. Although it would at 
first seem improbable that a compound like sodium chloride 
would thus exist in solution as free chlorine atoms and free 
sodium atoms, it can be conceived that neither of them would 
manifest active properties in presence of the other. We have 
analogous cases in the vapors of certain substances : that of 
ammonium chloride, for instance, is dissociated into free am- 
monia and hydrochloric acid, each of which masks the reactions 
of the other. Phosphorus pentachloride vapor is in like man- 
ner dissociated into phosphorus trichloride and chlorine. The 
theory is supported by many facts which cannot be given here. 
The conduction of the current is effected by the ions, which 
are thus continually united and dissociated through the mass 
of the liquid while those at the poles are set free. 

Faraday discovered the law expressing the relative quantities 
of the ions of different electrolytes that would be set free by a 
given current : it is, that a current of the same strength will 
set free quantities of the ions that are exactly proportional to 
their chemical equivalents. Referred to the elements, these 
quantities will be in the ratio of the atomic weights divided 
by the quantivalence. 

Action of the Metals upon the Salts. — The metals may 
displace each other in their saline solutions. 

If a plate of copper be plunged into a solution of silver 
nitrate, the copper enters into solution in the form of cupric 
nitrate, displacing and precipitating the silver. 

Cu + 2AgN0^ = Cu(N0^)2 + 2Ag 

Silver nitrate. Cupric nitrate. 

If a piece of iron be introduced into a solution of cupric 
sulphate, the iron instantly becomes covered with a layer of 



berthollet's laws. 277 

metallic copper, precipitated by a portion of the iron which 
enters the solution. 

Fe + CuSO* = Cu + FeSO* 

Cupric sulphate. Ferrous sulphate. 

If a strip of zinc around which some brass wires have been 
twisted be suspended in a dilute solution of plumbic acetate, 
the zinc will slowly displace the lead, which will be deposited 
in brilliant scales upon the brass wires. The latter gradually 
assume the appearance of fern-leaves, and the experiment 
constitutes the formation of the lead-tree. 

Richter, of Berlin, was the first to remark (1792) that the 
metals displace each other in their saline solutions without the 
neutrality of the latter being disturbed. When a neutral salt 
is precipitated by a metal, a new neutral salt results. The 
ferrous sulphate formed by the action of iron upon cupric sul- 
phate is neutral like the latter. 

It may be further stated that in this respect the chlorides 
behave like the oxygen salts. Iron displaces copper from cu- 
pric chloride as from the sulphate. In the first case it com- 
bines with CP, in the second with SO*, and in this circumstance 
again the latter group acts in the same manner as chlorine. 

CuCP + Fe =^ FeCP + Cu 

Cupric chloride. Ferrous chloride. 

Cu(SO^) + Fe = Fe(SO*) + Cu 

Cupric sulphate. Ferrous sulphate. 



BERTHOLLET'S LAWS. 

To conclude this general study of the salts, it only remains 
to indicate the actions exerted upon them by the acids and the 
bases, and the reciprocal actions of the salts themselves. These 
facts have been established and discussed principally by Ber- 
thollet, who demonstrated the influence of physical conditions, 
such as insolubility and volatility, upon the direction of chem- 
ical decompositions. 

Action of Acids upon the Salts. — When an acid, that is, a 
salt of hydrogen, is added to a metallic salt, the former tends 
to exchange elements with the latter, in such a manner as to 
form a new salt and a new acid. 

If sulphuric acid be added to powdered potassium nitrate, 
24 



278 ELEMENTS OF MODERN CHEMISTRY. 

the latter partially dissolves without the aid of heat, and 
potassium acid sulphate and nitric acid are formed. 

KNO^ -h ffSO* = HNO^ + KHSO* 

Potassium nitrate. Sulphuric acid. Nitric acid. Potassium acid sulphate. 

But this reaction is by no means complete. Powerful as 
are its affinities, the sulphuric acid cannot decompose the whole 
of the potassium nitrate unaided by heat ; a portion of the latter 
salt remains unaltered in presence of the excess of sulphuric 
acid, so that the resulting thick and fuming liquid really con- 
tains two acids and two salts, namely : 

Sulphuric acid. 
Nitric acid. 

Potassium acid sulphate. 
Potassium nitrate. 

The reaction takes place as if two acids were in presence of 
a single base. There is a conflict between the acids, and they 
tend to divide the base, which is potassium, in such a manner 
that each acid may saturate a portion. 

Hence the decomposition of potassium nitrate is not com- 
plete, and it is arrested as soon as the nitric acid set free can 
dispute with the sulphuric acid the possession of the base. 
There is then established a state of equilibrium between the 
two acids, both remaining in presence of the two salts. 

But this equilibrium is unstable and may be deranged by 
various circumstances. 

If the acid mixture be heated, abundant white vapors are 
disengaged. It is the nitric acid which volatilizes. But the 
sulphuric acid becomes thus preponderant in the liquid and 
decomposes another portion of potassium nitrate, and, if the 
volatilization of the nitric acid set free be not arrested by the 
removal of the heat, it is evident that nothing can prevent the 
complete decomposition of the potassium nitrate by the sul- 
phuric acid. The nitric acid, which by its presence alone 
prevented this total decomposition, is rendered powerless. 

Such is the influence of volatility or the gaseous state upon 
the progress of decompositions ; it is manifested in the highest 
degree in acids more volatile than nitric acid, such as carbonic 
and sulphurous acids. We have already seen that the carbon- 
ates and sulphites are easily and entirely decomposed by the 
energetic acids. 

While the volatility of acids favors the decomposition of 
their salts, insoluhility may play an analogous part. 



berthollet's laws. 279 

If hydrochloric acid be added to a solution of potassium sili- 
cate, a gelatinous precipitate of silicic acid is at once produced, 
and at the same time potassium chloride is formed. The de- 
composition is complete, for the silicic acid is insoluble. 

If sulphuric acid be poured into a solution of barium nitrate, 
a precipitate of barium sulphate is immediately formed, while 
at the same time nitric acid is set free. 

Ba(NO^)^ + ffSO* = 2HN0^ + BaSO* 

Barium nitrate. Sulphuric acid. Nitric acid. Barium sulphate. 

In this case also the decomposition is complete, for the ba- 
rium sulphate is insoluble. 

In these two reactions, the division of the base between the 
two acids cannot take place, since one of the products is imme- 
diately removed from the sphere of action by its insolubility. 
In the first case, it is the newly-formed acid which is precipi- 
tated ; in the second, it is the newly-formed salt which is de- 
posited in the insoluble state. 

Influence of Mass. — One other circumstance can influence 
the extent of these decompositions : it is the relative masses of 
the bodies which are in presence of each other. 

In the first experiment, it was supposed that an amount of 
sulphuric acid had been added to potassium nitrate sufficient to 
produce the double decomposition. If a large excess had been 
employed, it is evident that it would have become preponderant 
in the mixture, and that it would have displaced a more con- 
siderable portion of nitric acid. 

The influence of mass is manifested in the case of very feeble 
acids, and permits them to displace stronger acids. If a small 
quantity of tricalcic phosphate be introduced into water charged 
with carbonic acid, the latter, compensating by its mass for its 
deficiency in energy, will remove from the phosphate a portion 
of its base. Calcium dicarbonate and calcium acid phosphate 
are formed, both of which are soluble. 

Such, according to Berthollet, is the influence of insolubility 
and volatility upon the phenomena of double decomposition ; 
such, on the other hand, is the influence of mass. The same 
conditions intervene, and in the same manner, in the reactions 
which we are about to study. 

Action of Bases upon the Salts. — We will here consider 
only the action of the soluble bases, that is, the alkaline hy- 
droxides. 



280 ELEMENTS OF MODERN CHEMISTRY. 

If a solution of potassium hydroxide be poured into a solu- 
tion of sodium sulphate, no apparent change takes place ; but, 
according to the principle which has just been announced, it is 
probable that the potassium hydroxide has liberated a portion 
of sodium hydroxide. 

Na^SO* + 2K0H = K^SO* + 2NaOH 

Sodium sulphate. Potassium hydroxide. Potassium sulphate. Sodium hydroxide. 

But this decomposition cannot be complete, and the liquid 
must contain four bodies, namely : 

Sodium sulphate. 
Potassium sulphate. 
Sodium hydroxide. 
Potassium hydroxide. 

If potassium hydroxide be added to a solution of cupric sul- 
phate, a light-blue precipitate of cupric hydroxide is obtained. 
In this case the decomposition is complete, owing to the insol- 
ubility of the cupric hydroxide, which cannot dispute with the 
potassium hydroxide the possession of the acid. 

CuSO^ + 2K0H = K^SO* + CuCOH)^ 

Cupric sulphate. Potassium hydroxide. Potassium sulphate. Cupric hydroxide. 

If a solution of barium hydroxide be poured into a solution 
of potassium sulphate, a precipitate of barium sulphate is pro- 
duced, and potassium hydroxide remains in solution. In this 
case again, the decomposition is complete, by reason of the in- 
solubility of the barium sulphate. The potassium cannot di- 
vide the acid with the barium, for the latter escapes with all 
of it in the form of insoluble sulphate. 

K^SO* + Ba(OH)^ = BaSO* + 2K0H 

Potassium sulphate. Barium hydroxide. Barium sulphate. Potassium hydroxide. 

Action of the Salts upon each other. — The action of salts 
upon each other is what would naturally follow from the prin- 
ciples exposed in treating of the action of acids upon salts. 
Indeed, the latter possess the same constitution as the acids, 
and in their reactions upon salts should give rise to phenomena 
of the same order. These are exchanges of elements, double 
decompositions, which take place and are more or less complete, 
according to the physical conditions of the bodies which are 
produced, and also according to the relative masses of the re- 
acting bodies. 

In the first place, we must consider the reciprocal actions of 
the soluble salts, 



berthollet's laws. 281 

If a solution of cupric sulphate be treated with a solution 
©f sodium chloride, no precipitate is formed, but the blue color 
of the liquid is changed to green. This color is that of cupric 
chloride, and it may be supposed that the latter salt is formed 
by the reciprocal action of the sodium chloride and cupric 
sulphate. 

CuSO^ + 2NaCl = Na^SO* + CuCP 

Cupric sulphate. Sodium chloride. Sodium sulphate. Cupric chloride. 

But this interchange of elements between the cupric sulphate 
and the sodium chloride is arrested before the decomposition 
of the two salts is complete. A part of each remains unaltered 
in the presence of the other and of the two new salts which 
are formed. Consequently, the gi'een liquor obtained in this 
experiment contains four salts, namely : 

Cupric sulphate. 
Sodium chloride. 
Sodium sulphate. 
Cupric chloride. 

The respective proportions in which these salts exist in the 
mixture depend upon several circumstances. Malaguti has 
shown that in cases of this kind it is the energy of the affinity 
of the acids for the bases which governs the decomposition. 
The most energetic acid tends to combine with the most power- 
ful base, and the proportion of the salt thus formed predomi- 
nates in the mixture. Thus there is set up, as it were, between 
the elements in presence a sort of conflict, in which the stronger 
are victorious, while the weaker are not altogether annihilated. 
The result is a state of equilibrium which is only disturbed in 
case one of the products is by reason of its insolubility removed 
from the sphere of action of the other. The latter condition 
is realized in the following experiments. 

When barium chloride is added to the blue solution of cupric 
sulphate, a precipitate of barium sulphate is immediately formed, 
and cupric chloride remains in solution, coloring the liquid 
green. 

CuSO* + BaCF = BaSO* -f CuCP 

Cupric sulphate. Barium chloride. Barium sulphate. Cupric chloride. 

In this case the decomposition is complete, owing to the in- 
solubility of the barium sulphate. That salt is removed by 
cohesion from the sphere of action of the compounds which 
remain in solution. The portions first formed, and thus with- 

24* 



282 ELEMENTS OF MODERN CHEMISTRY. 

drawn, are replaced by others, and tlie reaction once commenced 
is finished in the same manner, so that the whole of the cnpric 
sulphate is converted into barium sulphate. 

A concentrated solution of common salt produces no precipi- 
tate in a concentrated solution of magnesium sulphate. How- 
ever, we must admit that there is an interchange of elements, 
and that the liquid contains four salts, namely : 

Magnesium sulphate. 
Sodium chloride. 
Sodium sulphate. 
Magnesium chloride. 

If this solution be exposed to an intense cold, it deposits 
crystals of sodium sulphate, while magnesium chloride remains 
in solution (Balard). Of the four salts which are in presence 
of each other, the sodium sulphate is the least soluble ; it is 
therefore deposited, and the double decomposition continues 
in the same manner until the greater part of the magnesium 
sulphate has been decomposed. 

The subject could be further developed by other examples. 
Those which have been given are sufficient to expose the true 
principle of double decomposition. 

We may add that if the operations be conducted in the dry 
way and at a high temperature, the volatility of the products 
which may be formed exerts an influence upon the reactions 
analogous to that which has been established for insolubility. 

If an intimate mixture of mercuric sulphate and sodium 
chloride be heated in a glass matrass, a sublimate of mercuric 
chloride is formed. 

HgSO* + 2NaCl = Na^SO* + HgCP 

Mercuric sulphate. Sodium cliloride. Sodium sulphate. Mercuric chloride. 

Action of Soluble Salts upon Insoluble Salts. — The study 
of double decomposition may be concluded by a summary ex- 
position of the action of soluble salts upon insoluble salts. It 
is analogous to that which has just been studied, that is, it is 
characterized by a tendency to an interchange of elements. A 
single example will be sufficient. 

If a solution of sodium carbonate be boiled for a long time 
with barium sulphate, it is found that the latter salt has under- 
gone a partial decomposition. It is partially converted into 
barium carbonate, insoluble like the sulphate, and the liquid 
becomes charged with a certain quantity of sodium sulphate. 
BaSO* -f Na^CO' = Na'^'SO* + BaCO^ 

Barium sulphate. Sodium carbonate. Sodium sulphate. Sarlum carbonate. 



NITRATES. 283 

This decomposition is more complete as the proportion of 
sodium carbonate which reacts upon the barium sulphate is 
increased. Here, as in some of the preceding experiments, the 
influence exerted by the greater mass is very appreciable. 

This study may be aptly terminated by summary indications 
upon the composition and properties of the more important 
classes of salts, which are the nitrates, sulphates, and carbonates. 

NITRATES. 

Composition. — Nitric acid containing HNO^, the nitrates 
contain the group NO^ combined with a metal which replaces 
the hydrogen of the acid. Consequently they contain one or 
more groups, NO^, according to the nature of the metal which 
has neutralized the nitric acid. Thus, 

1. KOH -f HNO^ = KNO^ + WO 

Potassium hydroxide. Nitric acid. Potassium nitrate. 

2. PbO + 2HN0^ = Pb(N0^)2 -}- H^O 

Plumbic oxide. Plumbic nitrate. 

3. gijo^ + 3HN0^ = Bi(N0^7 + 3H20 

Bismuth hydroxide. Bismuth trinitrate. 

With these few examples, we may conclude : 

1. That potassium, which unites with one atom of chlorine 
to form potassium chloride, KCl, unites also with one group, 
NO^, to form potassium nitrate. 

2. That lead, which unites with two atoms of chlorine to 
form plumbic chloride, PbCP, unites also with two groups, 
NO'^, to form plumbic nitrate. 

3. That bismuth, which unites with three atoms of chlorine 
to form bismuth trichloride, BiCP, unites also with three groups, 
NO^ to form bismuth trinitrate. 

In the chloride K'Cl potassium is monatomic. 

In the chloride Pb"C12 lead is diatomic. 

In the chloride Bi"'Cl3 bismuth is triatomic. 

In the nitrates, these three metals play the same parts as in 
the chlorides ; and we may say, in a general manner, that tbe 
metallic nitrates contain a metal united with as many times 
NO^ as the metal possesses atomicities. 

In K'(N03) monatomic potassium is united with NO^ 

In Pb"(]Sr03)2 diatomic lead is united to 2N03 

In Bi'"(N03)3 triatomic bismuth is united to SNO^ 

Such is the law of the composition of the nitrates. 



284 ELEMENTS OF MODERN CHEMISTRY. 

Properties. — All of the nitrates are soluble in water. Some 
of them are deposited from their solutions in the form of hy- 
drated crystals. Such is cupric nitrate, which crystallizes with 
six molecules of water at a low temperature. 

Others separate in anhydrous crystals. Such are the nitrates 
of potassium, sodium, silver, barium, and lead. 

All of the nitrates are decomposable by heat, and the pro- 
ducts of the decomposition vary with the nature of the nitrate 
and with the temperature. Thus, potassium nitrate is first 
converted into nitrite, and this is finally decomposed into 
nitrogen, oxygen, and potassium oxide. The nitrates of barium 
and lead yield nitrogen peroxide, oxygen, and a residue of 
oxide. Silver nitrate yields nitrogen peroxide, oxygen, and a 
residue of metal. 

2AgN0^ = 2N0' + 0' + 2Ag 

All of the nitrates liberate oxygen when they are heated; 
rich in oxygen, they constitute an abundant source of that 
element, and they are also easily reduced by bodies possessing 
a strong affinity for it. 

Sulphur, charcoal, phosphorus, and certain metals are ener- 
getically oxidized when heated with the nitrates. 

If sulphur be heated with potassium nitrate, potassium 
sulphate is formed, and sulphurous oxide and nitrogen are 
disengaged. 

2KN0^ -f S^ = K^SO* + SO^ + N^ 

Potassium nitrate. Potassium sulphate. 

When powdered potassium nitrate is thrown upon burning 
charcoal, the salt melts and increases the combustion of the 
charcoal, producing a vivid deflagration. Potassium carbonate 
is formed and carbon dioxide and nitrogen are disengaged. 

4KN0^ + 50 = 2K^C0=' + 3C0'^ + 2^^ 

Potassium nitrate. Potassium carbonate. 

Distinctive Characters. — All of the nitrates deflagrate when 
thrown upon incandescent charcoal. 

With concentrated sulphuric acid they evolve white vapors of 
nitric acid in the cold, and more abundantly when the reaction 
is aided by heat. When mixed with copper-filings and treated 
with concentrated sulphuric acid, they disengage red vapors. 

When the solution of a nitrate is mixed with its own volume 
of concentrated sulphuric acid, and a crystal of ferrous sulphate 
is introduced into the liquid, the crystal very soon assumes a 



StTLPHATES. 285 

brown color, which is communicated to the liquid. In this 
very delicate reaction the nitric acid is reduced by the ferrous 
sulphate to nitric oxide, which colors the excess of ferrous 
sulphate brown (page 164). 

The solution of a nitrate, when treated with sulphuric acid, 
will decolorize solution of sulphate of indigo when the liquid 
is heated to boiling. 

SULPHATES. 

Composition. — Sulphuric acid, H^SO*, contains two atoms 
of hydrogen capable of being replaced by a metal. When both 
are replaced by an equivalent quantity of metal, a neutral sul- 
phate is formed. An acid sulphate is formed when a single 
one of these atoms of hydrogen is replaced by a single atom of 
metal. The hydrogen of the acid is removed by the oxygen 
of the metallic oxide or hydroxide which more or less com- 
pletely saturates the sulphuric acid. Several cases may be 
presented. 

1. K'OH -f- H^SO* = g I SO* + H^O 



Potassium hydrate. 




Potassium acid sulphate. 




2. 2K'0H + 


ffSO* 


= K'^SO* 4- 

Potassium sulphate. 


2H=^0 


3. Pb"0 + 


H^SO* 


=: Pb"SO* + 


H^O 


Plumbic oxide. 




Plumbic sulphate. 






r H^so* 


(SO* 




4. (AP)-03 + 


] ffSO* 


= (AP)- } SO* + 


3ffO 




(H^SO* 


(_S0* 




Aluminium oxide. 


3 molecules. 


Aluminium sulphate. 





These examples show that all of the sulphates contain the 
group SO*, which in sulphuric acid is united with two atoms 
of hydrogen. This group is diatomic; it is necessary, then, 
that in the sulphates it shall be united with a quantity of metal 
equivalent to two atoms of hydrogen. 

1. In the acid sulphates it is united with an atom of hydro- 

gen and an atom of a monatomic metal, tt I SO*. 

2. It is united with two atoms of a monatomic metal in the 
neutral sulphates R'^SO*. 

3. With one atom of a diatomic metal in the neutral sul- 
phates M"SO*. 

These cases are very simple. It is not so, however, with 



286 ELEMENTS OF MODERN CHEMISTRY. 

the fourth, in which we consider the saturation of sulphuric 
acid by an oxide E^O^, such as ferric oxide or aluminic oxide. 
Each of the three atoms of oxygen of the oxide WO^ removes 
H^ from a molecule of H^SO*, and it results that the metal 
which was combined with 30", combines with 3(S0*)". The 
two atoms of metal which are substituted for 3H'^ in three mol- 
ecules of H^SO* are then equivalent to 6 atoms of hydrogen. 
They are hexatomic, as is marked by the index ^'. 

Properties. — The sulphates are nearly all soluble in water. 
Those of barium, strontium, and lead are insoluble. The sul- 
phates of calcium and silver, and mercurous sulphate are but 
slightly soluble. 

The alkaline sulphates, and those of calcium, barium, stron- 
tium, magnesium, and lead, are undecomposable by heat. The 
others are decomposed at a high temperature. A residue of 
oxide generally remains, while sulphur dioxide and oxygen 
are disengaged. The sulphates of zinc and copper are thus 
decomposed at a high red heat. 

CuSO'^ ^ SO^ + O + CuO 

Cupric sulphate. Cupric oxide. 

In case the oxide is reducible by heat, the residue consists 
of metal. 

HgSO* = Hg + SO^ + 0^ 

Mercuric sulphate. Mercury. 

The sulphates R\SO*/ are decomposed at a comparatively 
low temperature, disengaging vapor of sulphur trioxide and 
leaving a residue of sesquioxide. 

Fe\SO*)^ = Fe^O^ -j- 3S0=^ 

Ferric sulphate. Ferric oxide. Sulphuric oxide. 

The sulphates are readily deoxidized by carbon and other 
reducing agents. 

If an intimate mixture of potassium sulphate with an excess 
of charcoal be heated to bright redness, and allowed to cool out 
of contact with the air, a black powder is obtained, which pro- 
duces a shower of sparks when projected into the air. It is 
the pyrophorus of Gay-Lussac. It owes its spontaneous in- 
flammability on contact with the air to finely-divided potassium 
sulphide which it contains, and which attracts oxygen with great 
avidity. The sulphide is formed according to the following 
reaction : 

K^SO* + 4C = 4C0 + K^S 

Potassium sulphate. Potassium sulphide. 



CARBONATES. 287 

In the same manner barium sulphate and calcium sulphate 
are converted into sulphides by the action of charcoal at a high 
temperature. 

The other sulphates are also reduced under the same circum- 
stances, but the products vary; carbon dioxide or carbon mon- 
oxide and sulphurous oxide are disengaged, and the residue 
consists of either oxide or metal. 

Distinctive Characters. — When treated with sulphuric acid, 
the sulphates do not evolve any gas. They do not deflagrate 
when thrown upon burning charcoal. Their solutions give a 
white precipitate of barium sulphate with barium nitrate, which 
is insoluble in nitric acid. When this precipitate is washed, 
dried, and calcined with an excess of charcoal, it leaves a resi- 
due of barium sulphide, and when this is moistened with hy- 
drochloric acid, it evolves hydrogen sulphide, which is easily 
recognized by its odor, 

CARBONATES. 

Composition. — Carbonic acid is dibasic, like sulphuric acid. 
It is not known in the state of hydrate, and the carbonates are 
formed by the direct union of carbon dioxide with the metallic 
oxides or hydroxides. 

When freshly-burnt lime is exposed to the air, it attracts at 
the same time the moisture and the carbonic acid gas of the air, 
and is converted into carbonate. 

CO^ + CaO = CaCO^ 

Calcium oxide. Calcium carbonate. 

The carbonates then contain the group CO^ combined with 
a metal. In carbonic acid, this group would be united with two 
atoms of hydrogen. The composition of the more simple car- 
bonates is expressed by the following formulae : 

H^CO^ carbonic acid (unknown). 

R' ) 

TT [ C03 acid carbonates (dicarbonates). 

R'2C03 neutral carbonates. 
M"C03 neutral carbonates. 

In these formulae, R' represents a monatomic metal, such as 
potassium, which is equivalent to one atom of hydrogen. M" 
represents a diatomic metal, such as calcium, which is equiva- 
lent to two atoms of hydrogen. 

Properties. — Only the alkaline carbonates are soluble in pure 



288 ELEMENTS OE MODERN CHEMISTRY. 

water. The others are insoluble, but they dissolve in water 
charged with carbonic acid. 

The soluble carbonates possess an alkaline reaction. It is 
the same with the acid carbonates of the alkaline metals, which 
are ordinarily called bicarbonates, such as potassium acid car- 
bonate or bicarbonate of potassium. 

All of the carbonates except the alkaline carbonates are de- 
composable by heat. In this decomposition carbon dioxide is 
disengaged, and there remains a residue of oxide, or of metal 
in case the oxide be reducible by heat. Thus, the carbonates 
of magnesium, calcium, zinc, lead, and copper leave a residue 
of oxide after calcination ; silver carbonate leaves a residue of 
metal. 

Barium and strontium carbonates are but slowly decom- 
posed at a white heat ; their decomposition is facilitated by a 
current of steam, and easily effected in the electric furnace. 

Reducing agents, such as carbon and metallic magnesium, act 
upon the carbonates as upon the corresponding oxides : if the 
base be reducible, the metal is formed. 

If cupric carbonate be heated with charcoal, carbon dioxide 
is disengaged, and metallic copper remains. 

2CuC0^ + C = 3C0^ + 2Cu 

Cupric carbonate. Copper. 

In this experiment carbon dioxide is disengaged, for cupric 
oxide is easily reducible by charcoal. It is not the same with 
potassium oxide ; hence potassium carbonate is only reduced 
by charcoal at a very high temperature with disengagement 
of carbon monoxide. 

K^CO^ -f 2C = SCO + K^ 

When magnesium is substituted for the charcoal in this 
experiment, less heat is required to bring about the reaction, 
and the carbon as well as the potassium of the carbonate is 
reduced to the elementary state. 

K^^CO^ -f 3Mg = C + 2K + 3MgO 

All the carbonates are decomposed by phosphorus. 

A small piece of phosphorus may be placed at the bottom 
of a small test-tube, and the latter then nearly filled with well- 
dried sodium carbonate. The part of the tube containing the 
carbonate being heated to redness, the phosphorus may be 
heated so that its vapor will pass over the incandescent car- 



CLASSiriCATION OF THE METALS. 289 

bonate. The latter will be decomposed witli the formation of 
sodium phosphate and a deposition of carbon. After cooling, 
the contents of the tube will be black. 

The experiment may be repeated upon calcium carbonate. 
The phosphorus is placed in a small crucible, which is then 
introduced into a larger one. The calcium carbonate (chalk) 
is then placed upon the lid of the smaller crucible, which is 
pierced with holes. The arrangement is heated upon a double 
grate, so that when the chalk has been brought to incandes- 
cence, the vapor of phosphorus may be caused to pass through 
it by placing some hot coals upon the lower grate. The chalk 
is rapidly decomposed, carbon monoxide is disengaged, and a 
mixture of calcium phosphate and phosphide is formed. This 
mixture serves for the preparation of hydrogen phosphide. 

Distinctive Characters. — When treated with sulphuric acid, 
the carbonates disengage a colorless, incombustible gas, which 
extinguishes burning bodies and produces a milkiness when 
agitated with lime-water. 

CLASSIFICATION OF THE METALS. 

In the preceding pages we have studied the composition and 
the general properties of metallic compounds. This study has 
revealed the fact that the metals possess very different aptitudes 
to form compounds, and various capacities of combination, which 
are manifested by the greater or less number of other atoms 
which the atoms of these metals can attract. In this respect, 
the differences existing between the metals are analogous to 
those which we have already remarked between the non-metals. 
On comparing the metals among themselves, some are discov- 
ered which resemble each other in the general structure. of the 
compounds which they are capable of forming, and such can 
naturally be classed in the same group. On this plan the 
metals are divided into several families analogous to those first 
proposed by Dumas for the non-metals, and it will be seen that 
the general composition of the metallic compounds furnishes 
the elements for a natural classification of the metals. While 
this principle is excellent, its application is attended with some 
difficulties which chemistry has not yet been able to solve. 
Consequently, this chapter must be limited to summary indi- 
cations upon the subject. 

Some of the metals are incapable of combining with more 
N t 25 



290 



ELEMENTS OF MODERN CHEMtSTft"?. 



than a single atom of chlorine, bromine, or iodine. The com- 
pounds thus formed correspond in their atomic constitution to 
hydrochloric, hydriodic, and hydrobromic acids. On comparing 
potassium chloride or silver chloride to hydrochloric acid, it 
will be seen that an atom of potassium or an atom of silver 
occupies in them the place occupied by the hydrogen of the 
acid. The atoms of potassium and of silver are therefore 
equivalent to the atoms of hydrogen as far as their capacity 
of combination is concerned. The other alkaline metals, such 
as sodium and lithium, are similar and belong to the same group. 
Their chlorides, bromides, and iodides, which are arranged in the 
following table, present analogous compositions : 



MoNATOMic Metals. 


monatomic 
Chlorides. 


monatomic 
Bromides. 


monatomic 
Iodides. 


Potassium K' 


H'Cl 


EBr 


HI 


KCl 


KBr 


KI 


Sodium Na' 


NaCl 


NaBr 


Nal 


Lithium Li' 


LiCl 


LiBr 


Lil 


Silver Ag' ...... . 


AgCl 


AgBr 


Agl 



These metals form hydroxides or oxides whose atomic con- 
stitutions correspond to that of water, one or both of the 
hydrogen atoms of the latter being replaced by an equivalent 
amount of metal. In the same manner the hydrosulphides 
and monosulphides of these metals are derived from hydrogen 
sulphide. 





Type H20. 


Oxides. 


Hydroxides. 


K20?« 


KOH 


Na20 ?* 


NaOH 


Li20 


LiOH 


Ag20 





Type H2S. 



Monosulphides. Hydrosulphides. 
K2S KSH 

Na2S NaSH 

Li2S LiSH 

Ag2S 



The same analogy is continued among tne salts of these 



* The existence of these monoxides of potassium and sodium is rather 
doubtful. They are not obtainable from the hydroxides, carbonates, or 
nitrates by the action of heat, and the products resulting from the direct 
combination of the metals with oxygen appear to be very stable per- 
oxides of the types RO2 and BO. 



CLASSIFICATION OF THE METALS. 



291 



metals, as will be seen from the nitrates and sulphates which 
we take as examples. 

Nitric Acid, HNQS. Sulphueic Acid, HSSO*. 



Nitrates. 


Sulphates. 


Acid Sulphates. 


KNOS 


K^SO* 


KHSO* 


NaN03 


Na2S04 


NaHSO* 


AgN03 


Ag2S04 





It is seen that in all of these compounds the metals under 
consideration replace hydrogen atom for atom ; each of them 
possesses the same capacity of combination as that gas. They 
are said to be monatomic. 

Certain other metals manifest a double capacity of combina- 
tion; one atom of any of these is capable of replacing two 
atoms of hydrogen, consequently it can combine with two 
atoms of chlorine, bromine, or iodine, or with one atom of 
oxygen or sulphur. In the chlorides of these metals, the two 
atomicities of the metal are satisfied by the two atomicities of 
two atoms of chlorine. In their oxides, the two atomicities 
of the metal are satisfied by the two atomicities or bonds of 
affinity which reside in one atom of oxygen. These metals are 
then diatomic. They are quite numerous and can be divided 
into several groups, one of the most natural of which com- 
prises barium, strontium, calcium, and lead. The following 
table shows the constitution of the principal compounds of 
these metals : 



Diatomic Metals. 


Chlorides. 


Oxides. 


Nitrates. 


Sulphates. 


Barium Ba" . 

Strontium Sr" . 
Calcium Ca" . 
Lead Pb" . . 


2HC1 


H20 


2HN03 


H2S0* 


BaC12 
SrC12 
CaC12 
PbC12 


BaO 

SrO 
CaO 
PbO 


Ba(N03)2 
Sr(N03)2 
Ca(N03)2 
Pb(N03)2 


BaSO* 
SrSO^ 
CaSO* 
PbSO* 



The metals of this group combine with oxygen in two pro- 
portions, forming not only the monoxides, RO, but also the 
dioxides, ROl They thus form two oxides, while they are 
capable of forming but one chloride, RCP. Thus, barium 
forms a monoxide, BaO, a dioxide, BaO^, and a dichloride, 



292 ELEMENTS OF MODERN CHEMISTRY. 

BaCP ; but no tetrachloride of barium is known, and it is not 
probable that barium can act as a tetratomic element. How is 
it, then, that in the dioxide this metal can combine with two 
atoms of oxygen, while it cannot combine with four atoms of 
chlorine, which are equivalent to two atoms of oxygen ? In 
other words, what is the atomicity of barium in the dioxide 
which would seem to correspond to a tetrachloride? It is 
undoubtedly diatomic in the dioxide as it is in the monoxide, 
and the constitution of barium dioxide is analogous to that of 
hydrogen dioxide, which has already been indicated. The 
two atoms of oxygen mutually satisfy two of their atomicities 
by combining together, and they retain two which are neutral- 
ized in combining with the diatomic atom of barium. Thus, 
in barium monoxide one atom of oxygen is joined to one atom 
of barium by both of its atomicities ; in the dioxide two atoms 
of oxygen are united to one atom of barium, each by one atom- 
icity. If we represent the saturation of two atomicities by a 
straight line, as has before been explained, we will have the 
following formulae : 



Ba=:0 


Ba 


Barium monoxide. 


/\ 




0-0 




Barium dioxide. 



In this manner, theory enables us to fix the relations existing 
between the atoms in a given body. 

The comparison may be continued between the other diatomic 
metals. Magnesium, the radical of magnesia, somewhat resem- 
bles calcium in its relations, and forms, as it were, the centre 
of a group including magnesium, zinc, cobalt, and nickel, and 
which is called the magnesium group. Manganese and iron, on 
one hand, and copper, on the other, seem to join this group by 
certain of their characteristics. In their most stable and gen- 
erally their most important compounds, these metals act as 
diatomic elements. All form the dichlorides RCP and the 
oxides BO. But in other compounds, manganese and iron 
seem removed from the metals of this group, and resemble 
chromium and aluminium. Copper, which resembles magne- 
sium in the series of cupric compounds, approaches mercury 
and silver in the cuprous series. 

Bismuth, which might be classed with antimony, and gold 
are triatomic in their most important combinations. They 
form the chlorides BiCP and AuCP. 



CLASSIFICATION OF THE METALS. 



293 



A certain number of the metals may be grouped together as 
tetratomic^ since they manifest four atomicities in their principal 
combinations. They are tin, titanium, and zirconium. They 
form the chlorides RCP and the oxides K0^ In stannic chlo- 
ride, SnCl*, the tin is saturated with chlorine, of which it 
cannot combine with more than four atoms ; it is tetratomic 
in this saturated compound. But it may combine with only 
two atoms of chlorine, thus forming the chloride SnCP, which 
is not saturated, for it can still fix two more atoms of chlorine. 
Tin only manifests two atomicities in the dichloride. 

In the same manner, ferrous chloride, FeCP, can absorb 
chlorine, becoming ferric chloride. Above 700° the latter con- 
tains one atom of iron and three of chlorine, but just above 
its temperature of volatilization it appears to contain two atoms 
of iron united with six of chlorine. The two iron atoms would 
constitute a hexatomic couple ; the same peculiarity is presented 
by chromium and aluminium. 



Compounds. 


Chlorides. 


Oxides. 


Sulphates. 


Ferric 

Manganic 

Chromic 

Aluminic 


JFeCF or 
[ Fe2Cl6 
f MnCl3 or 
1 Mn2Ci6 
fCrCl3 or 
1 Cr2Cl6 
fAlCl3 or 
1 A12C1« 


Fe203 

Mn203 

Cr203 

A1203 


Fe2(SO*)3 
Mn2(SO*)3 
Cr2(S0*)3 
A]2(S04)3 



The following table gives a resume of the constitution of the 
principal metallic combinations. The metals there chosen as 
examples have different atomicities. 



Metals. 


Chlorides. 


Oxides. 


Nitrates. 


Sulphates. 


Monatomic metal— Potassium K' . 


KCl 


K20 


KN03 


K2S04 


Diatomic metal— Barium Ba" . . . 


BaC12 


BaO 


Ba(N03)2 


BaSQi 


Triatomic metal— Bismuth Bi"' . . 


BiC13 


Bi203 


Bi(N03)3 


Bi2(S04)3 


Tetratomic metal— Tin Sniv . . , 


SnC14 


Sn02 






Hexatomic group— (Fe2)Ti .... 


Fe2C16 


re203 


Fe2(N03)6 


Fe2(S04)3 
-.._. . ... J 



25* 



294 ELEMENTS OF MODERN CHEMISTRY. 

Such are the principles furnished by the theory of atomicity 
for a rational classification of the metals. 



Mendelejeff's Theory. 

Within recent years the labors of a Russian chemist, Men- 
delejeff, have developed interesting relations between the atomic 
weights and properties of the elements. He has shown that 
the properties are functions of the atomic weights, and that the 
functions are periodic. This relation is not applicable to a 
limited group of elements, but extends throughout the whole 
series, and consists not in certain analogies, but in the general 
physical and chemical properties taken together. 

If the elements be arranged in the order of their atomic 
weights, it will be noticed that these latter increase gradually 
by only a few units, and also that the properties of the elements 
are gradually modified with the increase in atomic weights. 
The modifications are not, however, continuously progressive, 
but are developed in several series. 

The difi'erences between the atomic weights of neighboring 
elements are not equal, but are nearly so, and where these 
differences are excessive it is probably owing to the existence 
of undiscovered elements. Mendelejeff predicted the existence 
of several such elements, and at least three of the gaps have 
since been filled by the discovery of gallium, scandium, and 
germanium. The hypothesis is then certainly worthy of seri- 
ous consideration in all attempts to classify the elements. 

The theory may be best explained by considering an example 
of the periodicity on which it rests. 

Let us study the first fourteen elements after hydrogen in 
the order of their atomic weights. 

Li = 7. Gl = 9. B = ll. C = 12. N = 14. = 16. F = 19. 
Na=23. Mg = 24. Al = 27. Si = 28. P = 31. S = 32. CI =35.5. 

We have here two groups, in each of which the change in 
physical and chemical properties is markedly progressive with 
the increase in atomic weight. The densities gradually increase 
to the middle of each series, and then decrease to the end. The 
atomic volumes, which are the quotients of the atomic weights 
by the densities, gradually decrease to the middle of the series, 
and then augment. The volatility also diminishes from sodium 
to silicon^ and again increases to the end of the series, 



CLASSIFICATION OF THE METALS. 295 





Na. 
. 0.97 


Mg. 

1.75 

14 


AL 

2.67 
10 


Si." 

2.49 

11 


P. 

1.84 
16 


S. 

2.06 

16 


01. 
1.8R 


Atomic volumes . . 


24 


27 



The atomicity, or combining capacity, as indicated by the 
number of atoms of hydrogen or chlorine with which one atom 
of the elements combines, displays a similar periodicity. 

LiCl GICP BCP CH* NH^ OH^ FH 

NaCl MgCP AlCP SiCP PH^ SH^ CIH 

The oxygen compounds show a similar progression. 

Li^O GPO' B^O^ C^O* N^O^ ^ 

Na^O Mg^O' APO^ SPO^ P^O^ S'O' CPO^ 

The number of oxygen atoms with which a constant number 
of atoms of elements of these series can combine, regularly 
increases, and the properties of the oxides undergo a gradual 
modification. Those at the beginning of the series form pow- 
erful bases ; the intermediate oxides are indifferent, while the 
latter members form strong acids. 

That which characterizes these variations is that they occur 
in the same manner in the two groups, so that the first member 
of the first series (Li) corresponds to the first member of the 
second. These two series form the first two periods of Men- 
delejeff, who has shown that these series or periods can be ex- 
tended throughout the whole list of elements, and that the 
properties of the ele7nents are in periodic relations with their 
atomic weights. 

The arrangement of the elements in the periodic system is 
shown in the table on the following page. The horizontal rows, 
consisting when complete of seven elements, are called periods, 
while the vertical columns constitute the natural groups. The 
series are sub-classified according to the number of the line, 
as odd and even. The members of each group are related by 
their atomicities, as well as by the isomorphism and some other 
properties of their compounds, but differ very materially in 
other respects. The fourth, the sixth, and the tenth periods 
are each followed by three elements having nearly equal atomic 
weights, and these nine elements constitute the eighth or transi- 
tional group. Hydrogen stands alone. The empty spaces in 
the table are probably the positions of elements yet to be dis- 
covered. The positions of argon and helium are unknown. 



296 



ELEMENTS OF 3I0DERN CHEMISTRY. 





























i 


f 




1 


SI'S 
03 9? 3 




M 






II 


S 




II 


0) o'd 




to 






s 




^ 


a.So3 










88§ 






4 


fH t- O 










II II 


II II' 




II II 










OJ o 


rs-o 












f^O 


«Ph 




OPM 


Hi 




S 
II 


II 


00 g 

s gi 


1 II 




: 
: 


i 

: 
: 




of the othe 
ivalence fo 
the first gr 
e together. 
















i|-5l 






CO 


i> 


i> 




. 


^ 


• 




2 


00 


i> 




: 




^<^rd" 


o 




§8 

IT 

o 


II 

CO 


00 

g II 

II ^ 

(-1 
O 


! « 

II 0) 

o H 




'• to 
II 


00 

"ll 
t3 


like the mem 
roup, but the 
; most marke 
ghts are very 






g 


05 


s « 

II M 




i S 


J2i 

o 

1— 1 
Eh 


> 


o 

II 


II 

Pi 


-1 II 

II ^ 


s 




. 


0^ o3 o 


< 




^ 




> 


;^ 


s 


H 






O 






00 


CO 


00 




: <35 


1— 1 
1— 1 

o 


> 




II 


g2 


S 




j 1 ^. 


ilar properti^ 
increases up 
The metalli 
ements who 


ill 


s 

o 


^ 1 

11 ^ 


§ II 

11 ^ 
II CC 


g 

J 


^ ?2 ^ g 






■rf 


o> 


'^^ 




: i> 


p possess Sim 
for oxygen i 
3 to the 8th. 
ree similar el 




pi 


05 

II 


o 

II 


II o 

CO 


eo 
II 5 


II 

1-1 


• S II 


















t>.CU.d 


Hi 


l_J 




CO 


^ s 


i> 


05 


: 1 




'"' 


SS 


(M 


II N 


CO "-I 


CO 






o 

II 
O 


II 


S5 II 

II 3 

CO 


CC 

1 




bo 
W 


























II 


85 


OJ II 


CD 

g II 

II t* 


CO 
tn 


: 


«o 

3 








o 




II o 


a '^ 


1 


<j 




aga)§ 






3 




W 


Ph 


o 


: 


: 




^l-T 


















i 














t^-rS^^ 






r-l <N 


eo 


■* o 


to l> 


00 


Ol O iH (M 


j^^S'SJ 




p3 












tH r-l i-i 




H 














O 3 02 




m 

















POTASSIUM. 297 

POTASSIUM. 

K = 38.82 
Potassium was discovered by Sir Humphry Davy in 1807. 
It ordinarily occurs in commerce in gray, globular masses, 
readily indented by tlie finger-nail. It has a dull, tarnished 
appearance, but when freshly cut it exposes a brilliant surface. 
Preparation and Properties. — Potassium is prepared by 
decomposing potassium carbonate by carbon at a high tem- 
perature. 

K^CO^ + 2C = SCO + K=^ 

Potassium carbonate. Carbon monoxide. 

The mixture is heated to whiteness in an iron retort and the 
vapors are passed into a copper receiver. The potassium dis- 
tils and condenses in globules or irregular masses, still contain- 
ing charcoal. It is purified by redistillation in an iron retort, 
and is condensed in a copper receiver filled with naphtha. 
The manufacture of potassium is a dangerous operation, 
owing to the formation of a very explosive compound of potas- 
sium and carbon monoxide, C^O^K^ (see page 697). Winkler 
has proposed a method of preparing the metal which consists 
in heating a mixture of potassium hydroxide and magnesium. 
2K0H -f Mg = MgO -f ff + 2K 

The hydrogen disengaged in this reaction facilitates the 
distillation of the potassium. 

Potassium melts at 62.5° (Bunsen). It boils at a red heat, 
and its vapor is green. When exposed to the air, it rapidly 
absorbs oxygen and at the same time decomposes the atmos- 
pheric moisture. It inflames at a temperature but slightly 
elevated and becomes converted into oxide. 

If a fragment of this metal be thrown into water, it at once 
takes fire and rushes about on the surface of the liquid, burn- 
ing with a violet flame. Finally, it disappears with a little 
explosion. 

This brilliant phenomenon is due to the energy with which 
potassium decomposes water. 

2W0 + K2 z= 2K0H + H^ 

The hydrogen which is disengaged is inflamed by the incan- 
descent metal. The potassium hydrate formed ultimately dis- 
solves in the water, but its temperature being very high at the 
moment of its solution, and its combination with the water 
also producing heat, there results a sudden formation of gteam, 
which gives rise to the little explosion, 



298 



ELEMENTS OF MODERN CHEMISTRY. 



POTASSIUM OXIDES. 

Potassium peroxide^ KO^ or K^O*, is formed when the metal 
is gently heated in a current of dry oxygen or air. It is an 
orange-colored substance which becomes darker on heating, 
and melts at about 280°, forming a dark-brown liquid. With 
water and with acids this peroxide reacts with violence, oxygen 
being disengaged, while hydrogen peroxide and potassium 
hydroxide or potassium salts are also formed. 

Potassium monoxide^ K2O, is not known in the pure state. 
The product resulting from the combustion of the metal in air 
appears to be a mixture of this oxide and the peroxide. 

POTASSIUM HYDROXIDE, OR CAUSTIC POTASH. 

This important compound is prepared by boiling 1 part of 
potassium carbonate with 12 parts of water, and gradually add- 
ing milk of lime to the boiling liquid. The lime combines 
with the carbonic acid, forming an insoluble carbonate, while 
the potassium hydroxide remains in solution. 

K^CO^ + Ca(OH)^ = CaCO^ + 2K0H 

Calcium hydroxide. Calcium carbonate. 

When the decomposition is finished the liquid is allowed to 
settle, and the clear solution decanted and rapidly evaporated. 




The residue is melted in a silver dish and poured out upon flat 
stone slabs or cast in cylindrical metallic moulds (Fig. 97). 

This product is known as potash by lime. It is impure. 
By treating it with alcohol, which dissolves only the potassium 



SULPHIDES OF POTASSIUM. 299 

hydrate, it may be purified from lime, and the salts of potas- 
sium it may contain, and especially the carbonate, which is 
formed by the absorption of carbonic acid gas from the air 
during the evaporation. The clear alcoholic solution is decanted, 
and after the alcohol has been expelled by distillation, the resi- 
due is evaporated to dryness and fused in a silver dish. It is 
known B,fi potash hy alcohol. 

Perfectly pure potassium hydroxide, such as is frequently 
required in the laboratory, is prepared by double decomposi- 
tion between potassium sulphate and barium hydroxide, the 
potassium hydroxide solution being separated by decantation 
from the insoluble barium sulphate. 

K^SO* + Ba(OH)^ = BaSO* + 2K0H 

Recently-fused potassium hydroxide occurs as opaque, white 
fragments having a short fibrous fracture and a density of 2.1. 
It melts at a red heat and volatilizes at whiteness ; it is not 
decomposed by heat. When exposed to the air, it absorbs moist- 
ure and carbonic acid gas, and deliquesces. It is very soluble 
in water, and produces heat in dissolving. A hydrate, KOH 
-|- 2H^0, is deposited from its hot and very concentrated solu- 
tion in acute rhombohedra. 

Potassium hydroxide is very caustic. It softens and destroys 
the skin, and for this purpose is employed in surgery as a caustic. 
It manifests the properties of an alkali in the highest degree ; 
these are its solubility in water, its power to neutralize the 
acids and decompose a great number of metallic solutions, and 
its corrosive action on the tissues. This alkalinity may be shown 
by the energy with which the most feeble solutions of potash 
restore the blue color to reddened litmus, and change to green 
the tincture of violets. 

SULPHIDES OF POTASSIUM. 

Potassium will burn in vapor of sulphur. It unites with 
the latter body in five difierent proportions, forming the sul- 
phides K^S, K'^S^ K^S^ K^SS and K^S^ 

Potassium monosvlphide is formed when potassium sulphate 
is heated to redness in a current of hydrogen, or in a brasqued^ 
and covered crucible with charcoal. 

1 A brasqued crucible is a clay crucible into whicb powdered charcoal 
moistened with gum-water has been strongly pressed, and afterwards cal- 
cined. The substance to be reduced is placed in a cavity hollowed out in 
the charcoal, 



300 ELEMENTS OF MODERN CHEMISTRY. 

K^SO* + 4C = 4C0 + K^S 

Potassium sulphate. Potassium monosulphide. 

A reddish, deliquescent, and caustic mass is thus obtained. 
When a mixture of sulphur and potassium carbonate is fused, 
carbon dioxide is disengaged, and a brown mass is obtained on 
cooling, which is known as liver of sulphur. It is a mixture 
of potassium polysulpliide with undecomposed carbonate and 
potassium sulphate or hyposulphite, according to the tempera- 
ture and the proportions of sulphur which have been employed. 
With an excess of sulphur, potassium pentasulphide is obtained. 
Liver of sulphur dissolves in water with a brown-yellow color. 

Potassium pentasulphide and hyposulphite are also formed 
when potassium hydrate is boiled with an excess of flowers of 
sulphur. The filtered solution is brown. When treated with 
hydrochloric acid, it evolves hydrogen sulphide, and finely- 
divided, yellowish, pulverulent sulphur is deposited. 
K^S^ + 2HC1 = 2KC1 + H^S -f S* 

POTASSIUM CHLORIDE. 

KCl 

This salt is found crystallized in cubes in the neighborhood 
of certain fissures of Vesuvius, and in thin layers in the saline 
deposits at Stassfurt, Prussia, and in other localities. At 
Stassfurt there is found a double chloride of potassium and 
magnesium, carnallite, KCl,MgCr^ -f- 6H^0. When this is 
dissolved in hot water, the greater part of the potassium 
chloride is deposited on cooling while the magnesium chloride 
remains in solution. 

Potassium chloride crystallizes in cubes, but it sometimes 
separates in octahedra from solutions containing free alkali. 
It is unaltered by the air. Its taste is more bitter than that 
of sodium chloride ; it is more soluble in water than the latter, 
and produces a greater depression of temperature in dissolving. 
1 part of chloride of potassium dissolves in 3 parts of water 
at 17.5°. 100 parts of water at 0° dissolve 29.23 parts of 
potassium chloride and 0.2738 additional for each degree of 
temperature. 

POTASSIUM IODIDE AND POTASSIUM BROMIDE. 

KI and KBr 
These compounds are important on account of their use in 
medicine and photography. Potassium iodide is obtained b^ 



POTASSIUM NITRATE. 301 

adding powdered iodine to a solution of potassium hydroxide 
until the latter is completely neutralized. Potassium iodide 
and iodate are formed, the latter being precipitated. The 
whole is evaporated to dryness, and the residue heated to red- 
ness, by which the iodate is converted into iodide. The mass 
is dissolved in hot water ; on cooling the solution deposits the 
iodide in fine colorless and transparent crystals. These crys- 
tals are opaque if the solution contains any free alkali. They 
are cubic and anhydrous. They melt at a red heat without 
decomposition ; their taste is salty and somewhat bitter. 100 
parts of water at 18° dissolve 143 parts of potassium iodide. 

A solution of potassium iodide dissolves iodine abundantly, 
assuming a dark-brown color. 

If nitric acid be added to a solution of potassium iodide, 
iodine is at once deposited and red vapors are disengaged if 
the solution be concentrated (page 141). 

This decomposition of potassium iodide takes place even in 
very dilute solutions. It may serve for the detection of the 
smallest trace of this salt if a solution of starch be previously 
added to the liquid ; in this case a blue color will be produced. 

Potassium bromide is prepared by a process similar to that 
which yields potassium iodide. It crystallizes in cubes which 
are soluble in about 1.5 parts of cold water. 

POTASSIUM NITRATE. 

KN03 

This important salt, long known as nitre and saltpetre, im- 
pregnates the soil and sometimes effloresces upon its surface in 
certain regions of India, Egypt, Persia, Hungary, and Spain. 
In the United States, it is found in many localities, generally 
in caverns in limestone rock, called saltpetre caves. It is 
obtained by lixiviating the earthy matters containing it and 
evaporating the solution. 

It is less abundant in northern climates. It is formed 
wherever nitrogenized organic substances decompose in pres- 
ence of potash. Thus, it exists in small quantities in the soil 
of cellars, in moist walls, and in old crumbling mortar. In 
these cases it is mixed with a certain quantity of sodium 
nitrate and a large excess of calcium and magnesium nitrates. 
Formerly such materials were lixiviated to obtain the nitrates, 
all of which were then converted into potassium nitrate. Nitre 
is also manufactured artificially by exposing to the air mixtures 

2t) 



302 ELEMENTS OP MODERN CHEMISTRY. 

of animal matters witli wood-ashes and lime which are fre- 
quently moistened with stale urine or stahle-drainings. By 
far the greater part of the saltpetre of commerce is now ob- 
tained from sodium nitrate, of which vast deposits occur in 
Chili and Peru. 

The conversion of this Chili saltpeter^ as it is called, into 
potassium nitrate is effected as follows. The recrystallized 
sodium nitrate is dissolved in water, and an equivalent 
molecular quantity of potassium chloride (obtained from 
Stassfurt salt) is added. The solution is boiled down until 
it attains a density of 1.5, when the hot liquid deposits 
sodium chloride, which is separated, and potassium nitrate 
crystallizes on cooling. 

Properties. — This salt crystallizes from its aqueous solution 
in. long, six-sided prisms, terminated by six-sided pyramids. Gen- 
erally these crystals are grooved or striated. They belong to the 
orthorhombic system. Their taste is cooling and slightly bitter. 

Potassium nitrate melts at about 350° ; at a higher tem- 
perature it disengages oxygen and is converted into potassium 
nitrite, KNO^, which is in its turn decomposed at a red heat, 
leaving a mixture of oxide and peroxide of potassium. 

Potassium nitrate is very soluble in hot water : 100 parts of 
water at 0° dissolve only 13.32 parts of the salt, but at 18° they 
dissolve 29 parts ; at 97°, 236 parts ; and at 100°, 246 parts. 

The facility with which potassium nitrate parts with its oxy- 
gen, of which it contains nearly half its weight, renders it an 
energetic oxidizer of many bodies. 

If a small quantity of pulverized saltpetre be thrown upon 
glowing coals, the salt melts and decomposes, increasing the 
combustion at the point of contact with the fuel : it is said to 
deflagrate. The nitrate becomes converted into carbonate. 

Ordinary black gunpowder is an intimate mixture of nitre, 
charcoal, and sulphur. Its average composition is 75 per 
cent, of nitre, 15 of charcoal, and 10 of sulphur. The com- 
bustion of this mixture is instantaneous, and gives rise to 
the sudden formation of gaseous products. The decomposi- 
tion may be expressed generally by stating that the char- 
coal combines with the oxygen of the nitre to form carbon 
dioxide and carbon monoxide ; the nitrogen is liberated, and 
the sulphur combines with the potassium, forming potassium 
sulphide. As the mixture contains all the oxygen necessary 
for its complete combustion, the latter can be efl"ected in a 



POTASSIUM SULPHATE — POTASSIUM CHLORATE. 303 

limited and closed space. It can readily be understood that 
the explosive energy of the powder is due to a sudden evo- 
lution of gas occupying many times the volume of the pow- 
der, and of which the volume is still further augmented by the 
high temperature. 

POTASSIUM SULPHATE. 

K2S0* 

This salt is obtained as a by-product in various industrial 
operations. It deposits from the mother-liquors of the soda 
from sea-weed when these are exposed to low temperatures. It 
may be made by saturating with potassium carbonate the potas- 
sium acid sulphate which is formed in the preparation of nitric 
acid by the decomposition of potassium nitrate with sulphuric 
acid, a process which is now but little employed. 

It crystallizes in four-sided prisms or in double, six-sided 
pyramids belonging to the orthorhombic system. These crys- 
tals are hard, anhydrous, unaltered by the air, and melt at a 
red heat without decomposition. They are but slightly soluble 
in water and insoluble in absolute alcohol. 100 parts of water 
at 0° dissolve 8.36 parts, and 0.1741 part for each additional 
degree of heat. 

POTASSIUM ACID SULPHATE. 

This salt may be obtained by fusing 13 parts of the neutral 
sulphate with 8 parts of concentrated sulphuric acid. The 
saline mass is dissolved in boiling water, and the solution when 
properly concentrated deposits rhombic octahedra or tabular 
crystals belonging to the orthorhombic system. 

Potassium acid sulphate is much more soluble in water than 
the neutral salt ; its solution is acid. When strongly heated, 
it first gives up water and then sulphuric oxide, leaving a resi- 
due of neutral sulphate. 

POTASSIUM CHLORATE. 

KC103 
This salt is formed, together with potassium chloride, by the 
action of chlorine upon a concentrated solution of potassium 
hydrate or carbonate : 

6C1 + 6K0H = KCIO^ -f 5KC1 -f 3H=^0 



304 ELEMENTS OF MODERN CHEMISTRY. 

It is less soluble than the chloride, and is consequently de- 
posited in great part as the solution becomes saturated with 
chlorine. It is purified by several recrystallizations. 

On a large scale it is obtained by the action of chlorine on milk 
of lime, and decomposing the resulting calcium chlorate with potas- 
sium chloride. ; 
6Ca(OH)2 -f 6CP = Ca(C103)2 + 5CaCP + GH^O 
and Ca(C103)2 + 2KC1 =: CaCP + 2KC103. 

Another process, recently introduced, depends upon the fact that 
an aqueous solution of potassium chloride is decomposed by the 
electric current into chlorine and potassium hydroxide which, under 
suitable conditions, will react and form the chlorate. 

Potassium chlorate crystallizes in colorless, monoclinic tables. 
When very thin they present an iridescent reflection. It melts 
at 360°, and at a higher temperature is decomposed into oxygen 
and chloride and perchlorate of potassium, the latter of which 
is also decomposed when the temperature is raised still further. 

2KC10^ = KCl + KCIO* + 0^ 
KCIO* = KCl -^ 0* 

Potassium chlorate deflagrates when thrown upon hot coals ; 
when mixed with sulphur, it explodes by friction or percussion ; 
the detonation becomes dangerous if the sulphur be replaced 
by phosphorus. 

It is not very soluble in cold water. 100 parts of water at 
0° dissolve 3.3 parts, and at 24°, 8.44 parts. It is much more 
soluble in boiling water. 

POTASSIUM PERCHLORATE. 

KC104 

This salt is formed by the action of either heat or sulphuric 
acid upon potassium chlorate (page 134). It is but slightly 
soluble in water, requiring 65 parts at 15° for its solution. It 
crystallizes in anhydrous and transparent right rhombic prisms. 
Above 400° it decomposes into potassium chloride and oxygen. 

POTASSIUM CARBONATES. 

Potassium Neutral Carbonate, K^COl — This carbonate 
is found in commerce under the simple name potash, and is 
known according to its source as Russian or American potash. 



POTASSIUM CARBONATES. 305 

It is obtained by lixiviating wood ashes; tbat is, exhausting 
them with water, evaporating the solution to dryness, and cal- 
cining the residue in the air. The potash thus obtained is 
impure carbonate mixed with other salts of potassium, princi- 
pally the chloride and sulphate, and small quantities of silicate. 
It contains from 60 to 80 per cent, of carbonate. 

Potassium carbonate is now manufactured from the native 
chloride, Stassfurt salt, by a process similar to that which will 
be described for the manufacture of sodium carbonate from 
common salt. 

Pure potassium carbonate may be prepared by calcining potas- 
sium acid tartrate, or cream of tartar, at a red heat. A black 
mass is thus obtained from which water dissolves pure potas- 
sium carbonate, and the solution is evaporated to dryness. 

Neutral potassium carbonate is very soluble in water, and 
absorbs moisture from the air. 1 part of the anhydrous salt 
dissolves in 1.05 parts of water at 3°, and in 0.49 parts at 70° 
(Osann). The solution has a decided alkaline reaction. A 
very concentrated hot solution deposits rhombic octahedra 
containing K^CO^ -|- 2H^0 on coohng. 

Potassium Acid Carbonate, KHCOl — When a current of 
carbonic acid gas is passed into a concentrated solution of potas- 
sium neutral carbonate, the gas is absorbed, and crystals of 
potassium acid carbonate, ordinarily known as bicarbonate of 
potash, are formed. 

It represents carbonic acid in which a single atom of hydro- 
gen is replaced by an atom of potassium. 

C02 + H20 == H2C03 carbonic acid (hypothetical). 
C02 + KHO = -n- [ CO^ potassium acid carbonate. . 
v€02 + K20 = K2C03 potassium carbonate. 

Potassium acid carbonate readily crystallizes in monoclinic 
prisms. It is much less soluble in water than the neutral 
carbonate, and its solution disengages carbonic acid gas on 
boiling. Its reaction is alkaline. 

Characters of Potassium Salts. — The salts of potassium 
communicate a violet tint to flame. Their solutions are not 
precipitated either by hydrogen sulphide, ammonium sulphide, 
or sodium carbonate. 

Perchloric acid occasions a white precipitate of potassium 
perchlorate. 

26* 



306 ELEMENTS OF MODERN CHEMISTRY. 

Platinum tetracliloride produces a yellow, crystalline precip- 
itate of platinum and potassium double chloride, 2KCl.PtCf*. 

Hydrofluosilicic acid forms a white, gelatinous precipitate 
consisting of potassium fluosilicate. 



SODIUM. 

Na = 22.88 

Sodium was discovered by Sir Humphry Davy in 1807. It 
was formerly obtained by a process analogous to that described 
for the preparation of potassium. An intimate mixture of 
sodium carbonate and charcoal was heated to whiteness in cast- 
iron cylinders, and the sodium vapor condensed in suitable 
vessels, carbon monoxide being disengaged. 

Na^CO^ +-2C r= 2Na + SCO 

For a number of years also the metal of commerce was 
manufactured by the more economical processes of Castner and 
Netto, in both of which it is extracted from sodium hydroxide. 
In Castner's process the reduction is effected by strongly heat- 
ing a mixture of the hydroxide and carbide of iron, CFe^ 

6NaOH + 2C = 2Na^C0^ -f SH^ + 2Na 

That of Netto consists in allowing fused caustic soda to 
trickle over incandescent charcoal contained in an iron retort. 
The sodium carbonate, formed as in the preceding equation, is 
drawn off at the bottom of the retort, while the metal is dis- 
tilled. 

At the present time the bulk of the sodium of commerce is 
produced by electrolysis of fused sodium chloride. 

2NaCl = 2Na + CP 

The salt used for this purpose is mixed with other chlorides 
— those of potassium and strontium are generally employed — 
in order to lower its melting point sufficiently to prevent 
the formation of a subchloride of sodium, and thus to increase 
the yield of metal. 

Sodium is soft at the ordinary temperature. It has a 
silvery lustre, melts at 96°, and boils at 742°. Its affinity for 
oxygen is less powerful than that of potassium ; it can be melted 
in the air without taking fire. When thrown upon water, it 



SODIUM. 307 

melts and runs around on the surface, producing a hissing 
noise. The water is decomposed with disengagement of 
hydrogen and the formation of sodium hydroxide. The re- 
action is analogous to that of potassium upon water, but is 
less energetic ; frequently, however, it terminates by an ex- 
plosion. 

When sodium is heated in a current of hydrogen, and the 
temperature maintained at 300°, the gas is absorbed, sodium 
hydride^ Na^H, being formed. This compound has the ap- 
pearance of silver, and a density of 0.96 ; at 240° it breaks up 
into its elements. 

OXIDES AND HYDROXIDE OF SODIUM 

Two oxides of sodium are known, a monoxide, Na^O, and a 
dioxide, NaO or Na^Ol The former has not been obtained in 
the pure state, but is probably one of the products of the action 
of metallic sodium upon the hydroxide. 

2Na -f. 2NaOH = 2Na^0 -f H^ 

Sodium hydroxide, NaOH, is frequently employed in the 
laboratory and in the arts under the name caustic soda. It is 
prepared by decomposing a rather dilute, boiling solution of so- 
dium carbonate by milk of lime, in the manner described for 
the preparation of potassium hydroxide (page 298). It occurs 
as a white solid, which attracts moisture and carbonic acid 
from the air, and finally becomes transformed into a dry mass of 
carbonate. Sodium hydroxide is freely soluble in water, and 
is very caustic. It is known in commerce as concentrated lye. 

Commercial caustic soda contains many impurities. The 
chemically pure hydroxide is best obtained by the action of 
metallic sodium upon water. For this purpose very small 
quantities of water and sodium are alternately introduced in 
a well-cooled and capacious silver dish. The resulting solu- 
tion is evaporated by heating, and the fused residue cast into 
moulds. 

Sodium dioxide, Na^O^ (sodium peroxide), is now produced 
on a commercial scale by heating the metal to 300° in a 
mixture of nitrogen and oxygen gases in which the propor- 
tion of the latter is gradually increased. It is a yellowish 
substance, and acts as a powerful oxidizing agent. Water 
decomposes it into hydrogen dioxide and sodium hydroxide. 
Its chief use is for bleaching silk and wool. 



308 ELEMENTS OF MODERN CHEMISTRY. 

SODIUM SULPHIDE AND HYDROSULPHIDE. 

Sodium sulphide^ Na^S, is prepared by the following proc- 
ess : A concentrated solution of sodium hydroxide is divided 
into two equal parts; one part is then saturated with hydrogen 
sulphide, sodium hydrosulphide being formed. 

NaOH + H^S = NaSH + H^O 

Sodium hydroxide. Sodium hydrosulphide. 

To this hydrosulphide the other portion of sodium hydroxide 
is added, and the solution is concentrated out of contact with 
the air. Hydrated crystals of sodium sulphide are deposited. 

NaSH + NaOH = WO -f Na^S 

These crystals are rectangular prisms terminated by four- 
faced points. When pure, they are colorless; they are very 
soluble in water. 

SODIUM CHLORIDE. 

NaCl 

This body is common salt, or sea-salt. It is widely diffused 
in nature. It is found in the solid state, as rock-salt, in large 
deposits in many countries. 

Sea-water contains a large proportion of sodium chloride, 
and this salt also exists in a number of mineral waters, of 
which it forms the most abundant constituent. 

Much of the salt of commerce is obtained by the evapora- 
tion of sea-water along the Mediterranean. The water is led 
into basins, where it forms a shallow layer, which is continu- 
ally swept by the summer winds. It thus becomes concen- 
trated, and is kept in motion from one basin to another, until 
it arrives in the areas where the salt is deposited. In many 
localities salt is obtained by direct mining operations ; more 
frequently, however, the crude salt is first dissolved in water, 
and after the insoluble residue has been separated the brine 
is evaporated. Thus, in Cheshire, England, bore-holes are 
sunk down to the salt bed, water is turned into these holes, 
and after it has become saturated with salt is pumped up 
and evaporated. 

Sodium chloride is also obtained by the evaporation of the 
waters of brine springs. The operation is conducted in large 
sheet-iron boilers ; the salt crystallizes from the hot liquid, 




SODIUM SULPHATE. 309 

and a double sulphate of calcium and sodium, which is but 
slightly soluble, incrusts the basins in the course of time. 

Sodium chloride crystallizes from its aqueous solution in 
cubes. The crystals are generally small, and a great number 
of them frequently become agglomer- 
ated in symmetrical hopper-like masses 
(Fig. 99). These crystals are anhy- 
drous, but contain a small quantity of 
interposed water ; when heated they 
decrepitate, because this water is vola- 
tilized and suddenly separates the crys- Fig. 99. 
tals. Sodium chloride fuses at a red 

heat and solidifies to a crystalline mass on cooling. It vola- 
tilizes at a white heat. It is very soluble in water, and its 
solubility increases only slightly with the temperature. Ac- 
cording to Gray-Lussac, 

1 part of common salt dissolves in 2.78 parts of water at 14° 
a u u 2.7 " " 60° 

a u (( 2.48 " " 109.7° 

The saturated solution boils at 109.7° ; its density at 8° is 
1.205. Sodium chloride is insoluble in absolute alcohol. 

SODIUM SULPHATE (Glauber's Salt). 
Na2S0* 

This salt is obtained in the arts by decomposing common salt 
with sulphuric acid (page 127). 

This operation, which constitutes the first step in the manu- 
facture of sodium carbonate, is conducted in a reverberatory 
furnace, connected with a suitable apparatus for the condensa- 
tion of the hydrochloric acid which is disengaged. Sodium 
acid sulphate is first formed, and at a higher temperature this 
reacts upon another molecule of sodium chloride. 



Na| 
HJ 



SO* + NaCl = Na^SO* + HCl 

Sodium acid sulphate. Sodium sulpliate. 

Sodium sulphate is now extensively produced by subjecting 
the mother-liquors from the manufacture of salt from sea-water 
to intense cold. 

It crystallizes from water in four-sided, oblique rhombic 
prisms, containing 10 molecules of water of crystallization j 



310 ELEMENTS OF MODERN CHEMISTRY. 

these crystals effloresce in the air. They possess a bitter, salty, 
and disagreeable taste. They are very soluble in water, and 
the temperature of their maximum solubility is 33°. Accord- 
ing to Gay-Lussac, 

100 parts of water at 0° dissolve 12 parts of sodium sulphate. 

« « 18° " 48 " " 

u (( 25° " 100 " " 

« .< 330 « 332.6 « (( 

(( « 500 (( 263 " " 

When the solution saturated at 33° is heated, it deposits an- 
hydrous sodium sulphate in orthorhombic octahedra, analogous 
to the anhydrous sodium sulphate found in nature {thenardite). 

Sodium Acid Sulphate, -^ \ SO*.— This salt may be ob- 
tained by dissolving in water the requisite proportions of so- 
dium neutral sulphate and sulphuric acid. On cooling the 
saturated solution, oblique rhombic prisms are obtained, which, 
according to Mitscherlich, contain two molecules of water of 
crystallization. These crystals are very soluble in water, and 
have an acid taste. Alcohol decomposes them into sulphuric 
acid, which dissolves, and neutral sulphate, which precipitates. 

SODIUM CAEBONATE. 

This important salt, known also as soda and soda ash, is 
manufactured on an immense scale in the arts. It is used in 
the manufacture of soap and glass, for washing, and many 
other purposes. It was formerly obtained from the ashes of 
fuci, algae, and other sea-plants which furnished Alicant soda. 
It is now most generally prepared from sodium chloride. One 
process, which is due to Le Blanc, consists of three distinct 
operations: 1st, the transformation of the sodium chloride 
into sulphate by sulphuric acid ; 2d, the conversion of the sul- 
phate into carbonate by calcination with a mixture of chalk 
and coal; 3d, lixiviation of the calcined mass and evaporation 
of the solution. Only the latter two operations need be de- 
scribed here : they are conducted in reverberatory furnaces, 
of which the doubly-arched roofs are licked by the flame of 
the combustible (Fig. 100). 

A mixture of 1000 parts of sodium sulphate, 1040 parts of 
chalk, and 580 parts of coal is first introduced into compart- 



SODIUM CAEBONATE. 



311 



ment B of the furnace, where it is dried. It is then transferred 
to compartment A, where the temperature is very elevated, 
and where the sodium sulphate is reduced to sulphide by the 




Fig. 100. 

coal. The sodium sulphide and chalk react upon each other, 
forming sodium carbonate and calcium sulphide (Kolb). 

The results of the reaction may be expressed by the follow- 
ing equation : 

Na^SO* + CaCO^ + C^ = XaTO^ + CaS + 4C0 

There are, however, certain secondary reactions which talie 
place at the same time ; thus, a certain quantity of sodium 
oxide is formed by the action of the coal upon the carbonate. 

Na^CO^ -{- C == 2C0 + Na^O 

When the incandescent mass has become pasty, it is removed 
from the farnace. reduced to powder, and thoroughly lixiviated. 
The water dissolves the sodium carbonate, and leaves the in- 
soluble calcium sulphide, which remains mixed with the lime 
produced by the decomposition of the excess of chalk employed 
(Grossage, Scheurer-Kestner). The solutions are concentrated 
in the boiler D, heated by the waste heat from the soda fur- 
nace. Finally, they are drawn off into the compartment C, 
where they are evaporated to dryness. The soda ash of 
commerce is thus obtained. When the properly-concentrated 
solution is allowed to cool, the crystallized soda (washing 
soda) of commerce is deposited. 

Another process, known as the ammoiiia-soda process, has 
not only entered into successful competition with that of 
Leblanc, but appears to gradually supersede it. It is also 
known as Solvay's process. 



312 ELEMENTS OF MODERN CHEMISTRY. 

It depends upon the double decomposition whicli takes place 
between ammonium acid carbonate and sodium chloride in 
concentrated aqueous solution. 

NaCl + (NH*)HCO^ = NH*C1 + NaHCO^ 

The sodium acid carbonate, which is but slightly soluble, is 
precipitated ; it is collected and converted into the neutral car- 
bonate by the action of heat. 

2NaHC0^ = Na^CO^ + CO^ + H^O 

It thus loses half of its carbonic acid, which is utilized for 
the preparation of a new quantity of ammonium acid carbonate. 
The other portion of the carbonic acid necessary for this oper- 
ation is produced by the calcination of lime-stone (calcium car- 
bonate), which at the same time yields the lime necessary for 
the liberation of the ammonia contained in the mother-liquor 
in the form of ammonium chloride. 

A considerable quantity of sodium carbonate is also manufac- 
tured from cryolite^ which is a double fluoride of sodium and 
aluminium, and of which large deposits exist in Greenland. 
The mineral is calcined with lime, calcium fluoride and alumi- 
nate of soda being formed. 

2AlFl3NaF -f 6CaO = 6CaF^ -f AP0^3Na^0 

Cryolite. Calcium fluoride. Aluminate of soda. 

The latter compound is dissolved out by water and decom- 
posed by carbonic acid gas, aluminium hydroxide being pre- 
cipitated and sodium carbonate remaining in solution. 

Sodium carbonate crystallizes in monoclinic prisms, con- 
taining 10 molecules of water of crystallization. When 
heated, they fuse in this water of crystallization, which they 
then abandon ; they also lose it by efflorescence when exposed 
to the air. 

Sodium carbonate is very soluble in water, and the solution 
has a strongly alkaline reaction. According to Poggiale, 

100 parts of water at 0° dissolve 7.08 parts of sodium carbonate. 
" " 10° " 16.06 " « 

" " 20° " 25.93 « " 

« " 25° " 30.83 " « 

" " 30° " 35.90 " " 

" " 104.6° " 48.5 " " 

The saturated solution boils at 104.6°. Sodium carbonatQ 
is insoluble in alcohol, 



SODIUM BORATE. 313 

Sodium Acid Carbonate, NaHCO^— When carbonic acid 
gas is passed into a solution of sodium carbonate or over 
crystals of that salt, the gas is absorbed and sodium acid car- 
bonate, commonly called bicarbonate of soda, is formed. This 
salt crystallizes in oblique, four-sided prisms, shortened into the 
form of tables. Its taste is salty and slightly alkaline. It is 
less soluble in water than the neutral carbonate. It restores 
the blue color to reddened litmus ; its solution does not pre- 
cipitate that of magnesium sulphate, and when boiled loses 
carbonic acid, neutral carbonate being formed. 

PHOSPHATES OF SODIUM. 

There are three phosphates of sodium derived from ordinary 
or otho-phosphoric acid. 

H) Na") Na^ Na") 



H ^ PC* H ^ PC* + 2H20 Na )■ PC* + 12H20 Nsi } PO* + 12H20 

hJ hJ hJ NaJ 

Phosphoric Monosodium Disodium phosphate. Trisodium phosphate, 

acid. phosphate. 

Monosodium phosphate reddens blue litmus ; the disodium 
and trisodium salts have an alkaline reaction. The most 
important in the arts and in commerce is disodium phosphate, 
or common phosphate of soda. It is prepared by neutral- 
izing the calcium acid phosphate, obtained by digesting 
bone-dust with dilute sulphuric acid and filtering, with so- 
dium carbonate. Tricalcium phosphate is precipitated, and 
disodium phosphate remains in solution.- By evaporation of 
the filtered liquid, the salt may be obtained in voluminous, 
transparent, monoclinic prisms, containing 12 molecules of 
water of crystallization. Monosodium phosphate exists in 
urine, and is the cause of the normal acidity of that excretion. 

SODIUM BORATE, OB BOBAX. 

This salt corresponds to tetraboric acid, containing 2B^0^ -f- 
H^O = H'^B^O^ It results from the action of one molecule 
of sodium oxide upon two molecules of boric oxide. 
2(B'0') -f Na^O = Na^B^O^ 
It crystallizes with either 10 or 5 molecules of water. 
Borax was formerly obtained from Asia, where it exists in 
solution in the waters of certain lakes. By the evaporation 
o 27 



314 ELEMENTS OF MODERN CHEMISTRY, 

of these waters a product known as tinkal was obtained ; this 
is natural borax. Part of the borax of commerce is obtained 
by saturating the boric acid of Tuscany with sodium carbo- 
nate, and evaporating the solution below 56°. Borax is found 
in abundance in certain lakes in California, and large quanti- 
ties are now derived from the naturally occurring borates of 
calcium (colemanite and horocalcite) and magnesium (bora- 
cite). These yield borax by double decomposition with 
sodium carbonate. When a concentrated boiling solution of 
borax is allowed to cool, it deposits between 79° and 56° 
regular octahedral crystals containing 5 molecules of water 
of crystallization ; below 56° the crystals deposited are 
rhombic prisms and contain 10 molecules of water. The 
latter form is that found in commerce. Borax solution is 
faintly, alkaline. 

When borax is heated, it melts in its own water, swells up 
and becomes dry, and then undergoes igneous fusion. Melted 
borax dissolves a large number of oxides, forming borates. 
On solidifying, the color and appearance of a number of these 
are highly characteristic. For this reason borax is a valuable 
agent in analysis. Anhydrous borax dissolves in 12 parts 
of cold and 2 parts of boiling water. 

Borax possesses antiseptic properties and is used as a 
preservative. 

Characters of Sodium Salts. — Sodium salts are not pre- 
cipitated from their solutions by either hydrogen sulphide, 
ammonium sulphide, sodium carbonate, or platinic chloride. 
Hydrofluosilicic acid forms with them a white precipitate. A 
solution of potassium antimonate produces a white precipitate 
of sodium antimonate (Fremy). 

Sodium salts impart a yellow color to non-luminous flames. 

A small quantity of alcohol may be ignited in a saucer and 
will burn with an almost colorless flame, but the introduction 
of a small quantity of sodium hydrate, chloride, or any other 
sodium compound, at once colors the flame bright yellow. 

This character is very sensitive, and the smallest trace of 
sodium may thus be recognized by introducing a platinum wire, 
dipped into the substance to be tested, into the colorless flame 
of the blow-pipe or of a Bunsen burner. 



LITHIUM — CESIUM AND RUBIDIUM. 315 



LITHIUM. 

Li = 6.97 

In 1817, Arfvedson, a Swedish chemist, discovered a new 
alkali, lithia, which is the hydroxide of lithium, LiOH, anal- 
ogous to potassium hydroxide, KOH. To this hydroxide cor- 
responds an oxide, Li^O, and a chloride, LiCl. Bunsen was the 
first to obtain the metal lithium, which he prepared by electrol- 
ysis of the fused chloride. It is a silvery-white metal, but its 
surface rapidly tarnishes in the air. It is the lightest of the 
solid elements, its density being between 0.578 and 0.589. It 
melts at 180°. It is less oxidizable than either sodium or 
potassium. When heated above its point of fusion in the air or 
in oxygen, it burns with a brilliant white flame. It decomposes 
water at ordinary temperatures, but without melting like sodium. 

The salts of lithium are soluble in water, but the carbonate 
and phosphate only slightly so. There exists also a double 
phosphate of sodium and lithium, which is but slightly soluble. 
The salts of lithium communicate a red color to the flame of 
alcohol or of the Bunsen burner. 

The compounds of lithium are generally prepared from 
lepidolite^ tripJiyline^ aniblygonite^ or spodumene^ minerals of 
complex composition containing small amounts of the ele- 
ment in the form of silicate or phosphate. 



CESIUM AND RUBIDIUM. 

SPECTRUM ANALYSIS. 

Cesium and rubidium are two alkaline metals discovered 
by Kirchhoff" and Bunsen in 1860-61, by the aid of a new 
method of analysis. This method consists in the examination 
of spectra ; hence the name spectrum analysis. 

The solar spectrum formed upon a screen which intercepts a 
beam of solar light refracted by passage through a prism, con- 
sists of a series of colored bands. The different simple rays 
of which white light is composed are unequally refracted by 
the prism, and separate from each other on their emergence. 
The violet rays, which are farthest turned from their original 
direction, form the most deviated extremity of the spectrum. 



316 ELEMENTS OF MODERN CHEMISTRY. 

The red rays, which are the least refracted, form the least de- 
viated extremity. The visible spectrum of solar light presents 
not only a succession of variously-colored bands ; when it is 
closely examined by the aid of magnifying instruments, it is 
found that the succession is not continuous, but that the lumi- 
nous bands are traversed by dark lines. These lines, which 
were discovered by Wollaston. and studied by Fraunhofer, are 
very numerous, and are irregularly distributed throughout the 
spectrum, from the red to the violet, but each one of them 
occupies a definite position, and for the principal lines that 
position has been determined by exact measurements. Fraun- 
hofer designated them by the letters A, B, C, D, E, F, Gr, H. 
The D line is the most distinct of all : its place is in the yel- 
low. Other lights, the stars, for example, give similar discon- 
tinuous spectra. On the contrary, an incandescent platinum 
wire, or any other luminous source which contains no volatile 
matter, gives a continuous spectrum. 

Very interesting facts are observed when the sources of light 
are flames into which the vapors of volatile substances, par- 
ticularly the metallic salts, are introduced. The spectra of such 
flames are formed exclusively of brilliant lines (see plate). 

If a platinum wire which has been dipped into a solution 
of sodium chloride be introduced into the colorless flame of 
a Bunsen burner, the flame will assume a yellow color, and will 
give a visible spectrum, but one which is very incomplete, 
since it consists of a single yellow line. It has been found 
that this line exactly coincides with the dark line D, existing in 
the yellow of the solar spectrum. This line characterizes 
sodium in all of its compounds : it is the spectrum of sodium. 

In the same manner, a flame into which a compound of potas- 
sium, lithium, barium, calcium, or other volatile metal is intro- 
duced, will give for each metal a particular spectrum formed of 
variously-colored lines. Each is perfectly characterized by the 
number, color, and position of the lines. Barium gives the most 
numerous and the widest lines ; other metals give more compli- 
cated spectra. That of iron is composed of 70 brilliant lines. 

Kirchhofi* and Bunsen, who discovered these facts, made a 
happy application of them to analysis. To detect the presence 
of a metal in a compound or even in a mixture, a small portion 
of the substance is introduced into a colorless gas flame, and 
the spectrum then given by the flame is observed by the aid of 
an instrument called a spectroscope. The light to be examined 



SILVER. 317 

is caused to pass through a narrow rectangular slit before falling 
on the prism. The image of the slit is then refracted to its own 
peculiar place in the spectrum. 

The method is so sensitive that -g-.-ooT.Too- ^f a milligramme 
of sodium chloride will render the yellow sodium line distinctly 
visible. The discovery of two new metals, caesium and rubi- 
dium, crowned the brilliant researches of Kirchhoff and Bunsen. 

Since then, a number of new metals have been discovered 
by the aid of spectrum analysis : thallium, which gives a 
green line, indium, which gives an indigo-blue line, gallium, 
which gives two violet lines very close together, and several 
others which will be mentioned farther on. Spectrum analy- 
sis has been useful also in the discovery and characterization 
of the new gaseous elements, argon, helium, and krypton. 



SILVER. 

Ag (Argentum) = 107.11 

Natural State. — Silver is found native and in combination 
in many minerals. Among these are the sulphide, the sulph- 
antimonides and sulpharsenides, the antimonide, chloride, 
bromide, iodide, selenide, telluride, and lastly an amalgam 
of silver. It is found in small proportions in many galenas 
and copper pyrites. 

Treatment of Silver Ores. — According to the nature of 
the ores the extraction of the silver is effected in the dry way 
or the wet way. 

Argentiferous galena is reduced as described under lead, 
and the metal which contains all the silver is remelted and 
subjected to the process of cupellation (page 345), whereby 
the lead is removed as oxide, and the silver remains in the 
metallic state. 

In case the lead contains but a very small proportion of 
silver, a process devised by Parkes is employed ; it depends 
on the fact that when melted lead containing silver is agitated 
with a small proportion of zinc, the latter metal dissolves out 
all the silver, and the resulting alloy rises to the surface in 
the form of a scum. This is readily collected and the zinc 
and lead are removed, the first by distillation, the last by 
cupellation. 

27* 



318 ELEMENTS OF MODERN CHEMISTRY, 

When the silver ore is free from lead, the extraction of 
the silver may be accomplished by means of mercury ; an 
amalgam of silver is formed from which the mercury is sepa- 
rated by distillation. 

Mexican Amalgamation or Patio Process. — American silver 
ore consists of sulpharsenide and sulphantimonide of silver, 
mixed with silver chloride and native silver, the whole being 
disseminated in silica, calcium carbonate, and ferric oxide. 
In Mexico, the following primitive process is still used. The 
finely-pulverized ore is mixed with two per cent, of common 
salt and thrown into circular areas paved with flag-stones, 
where it is rendered homogeneous by being trodden for several 
hours by mules. About one per cent, of copper pyrites which 
has been roasted in the air and contains cupric sulphate is 
then added. The latter salt reacts with the sodium chloride, 
forming sodium sulphate and cupric chloride, which latter 
decomposes the silver sulphide, forming silver chloride and 
cupric sulphide. Mercury is then added and reduces the 
silver chloride, with formation of chloride of mercury and 
metallic silver. During the whole time the mass is continually 
trodden by the mules, and the mercury comes in contact with 
the disseminated silver : the amalgam formed solidifies in 
about a fortnight. A second and finally a third addition of 
mercury is then made until 7 or 8 parts of that metal have 
been employed for one part of silver to be extracted. After 
a few months, the operation is terminated, and the mass is 
washed with large quantities of water to remove the earthy 
and salty matters. The amalgam remains, and is heated in 
order to extract the silver. 

American or Washoe Process. — The above method of ex- 
traction is too slow to be employed for the vast quantities of 
silver ore that are mined on the Pacific Slope. The ore is 
there crushed and roasted with sodium chloride and a small 
proportion of cupric sulphate, in furnaces of a peculiar con- 
struction. By this means all of the silver is converted into 
chloride. The mass is made into a pulp with water and agi- 
tated with mercury in large tanks or " pans." The silver 
chloride is reduced as before, and the amalgam obtained is 
first squeezed out and afterwards heated to expel the mercury. 
To this end it is placed in horizontal iron retorts (Fig. 102), 
which are heated to cherry redness. The mercury distils 
and is collected under water, while an impure silver remains. 



SILVER. 



319 




Fig. 102. 



Silver may also be extracted in the wet way. The Patera 
process, which is applicable to sulphide ores, consists in trans- 
forming the silver into 
chloride by roasting the 
ore with salt, and lixivi- 
ating the product with so- 
dium thiosulphate. Sul- 
phide of silver is then 
precipitated by adding an 
alkaline sulphide to the 
solution. 

Ziervogel's process de- 
pends on the conversion of 
sulphide of silver into sul- 
phate by roasting the ore 
in the air. Upon treating 
the mass with hot water, 

the silver sulphate passes into solution, from which the metal 
may be precipitated by metallic copper. 

Properties. — Silver is the whitest and most brilliant of all 
the ordinary metals. Next to gold, it is the most malleable 
and the most ductile. Its density is 10.5. It is the best 
conductor of heat and electricity. 

It melts towards 1000°, and when fused has the curious 
property of dissolving oxygen, of which it absorbs 22 times 
its volume. On solidifying, it again disengages the gas ; this 
phenomenon, which occasionally causes the projection of por- 
tions of silver, is called spitting. Silver volatilizes at the high 
temperatures of the oxyhydrogen blow-pipe and the electric 
furnace. Its vapor is green. 

It is unaltered by the air. In the presence of moisture, it 
is acted upon by ozone, being converted into the peroxide, AgO 
or Ag^Ol 

It decomposes concentrated solution of hydriodic acid, dis- 
engaging hydrogen and forming silver iodide (Deville). Hy- 
drochloric acid only attacks it superficially. Hydrogen sulphide 
blackens it, forming a pellicle of silver sulphide. Its best sol- 
vent is nitric acid which attacks it in the cold, yielding silver 
nitrate and disengaging red vapors. 

The alkalies have no action upon silver; for this reason, silver 
vessels are used for fusing potassium hydroxide and concen- 
trating its solution. 



320 Elements of modern chemistry. 

By precipitating silver solutions witli various reducing agents, 
under peculiar circumstances, Carey Lea has obtained interest- 
ing allotropic forms of silver, red, blue, and gold in color, and 
having a high degree of lustre. They are readily reconverted 
into ordinary silver. 

SILVER OXIDE. 

Ag^O 

The only important oxide of silver is the monoxide, which 
is precipitated in the anhydrous state when potassium hydrate, 
free from chloride, is added to a solution of silver nitrate. 

It forms an olive-brown, flocculent deposit which yields a 
brown powder on drying. 

Silver oxide is readily decomposed by heat into silver and 
oxygen. It is reduced by hydrogen at a temperature below 
100°. When recently precipitated, it is slightly soluble in 
water. It is an energetic base, perfectly neutralizing the acids, 
and displacing cupric oxide from the cupric salts. 

When oxide of silver is digested with ammonia it is con- 
verted into a very explosive, black powder, known as fulmi- 
nating silver. It appears to be the nitride Ag^N. 

SILVER SULPHIDE. 

To the oxide of silver corresponds the sulphide Ag^S, which 
occurs native, as argentite, crystallized in regular octahedra, 
ordinarily modified by facettes. It is soft and can be scratched 
by the finger-nail. Silver and sulphur combine readily by the 
aid of heat. 

SILVER CHLORIDE. 
AgCl^ 

This body is found native and is known to mineralogists as 
horn-silver. It is sometimes found crystallized in cubes and 
octahedra. It is formed directly when silver is heated in chlo- 
rine gas, and is prepared by double decomposition by adding 
hydrochloric acid or a solution of sodium chloride to solution 
of nitrate of silver. A white, curdy precipitate is thus obtained, 
which assumes a violet tint when exposed to the action of light. 
The change of color is due to partial decomposition. 

Silver chloride melts at about 260°, and solidifies on cooling 
to a gray, horn-like mass that can be cut with a knife. 

If recently precipitated and moist silver chloride be placed 
upon a sheet of zinc, in a short time a dark color will appear 



SILVER IODIDE — SILVER NITRATE. 321 

on tlie borders of the chloride, and the whole of that body will 
soon be converted into a dark-gray powder of finely-divided 
silver. Zinc chloride is at the same time formed. 

This reaction takes place much more rapidly if the silver 
chloride be moistened with hydrochloric acid. In this case 
the reduction is eifected by nascent hydrogen produced by the 
action of the hydrochloric acid on the zinc. 

When silver chloride is fused with the alkaline hydrates or 
carbonates, it is reduced to metallic silver : oxygen is disen- 
gaged, and an alkaline chloride is formed. 

Recently-precipitated silver chloride dissolves readily in aque- 
ous ammonia. When dry, it absorbs ammonia gas abundantly, 
and Faraday employed this compound for the preparation of 
liquid ammonia. 

Silver chloride dissolves also in alkaline hyposulphites. 

SILVER IODIDE. 
Agl 
Silver iodide is obtained as a yellow precipitate by adding 
potassium iodide to a solution of silver nitrate. It blackens 
on exposure to light. It is but very slightly soluble in ammo- 
nia, a property which distinguishes it from silver chloride. 

SILVER NITRATE. 

AgNQs 

This salt is prepared by dissolving silver in nitric acid. If 
the metal be pure, a colorless solution is obtained which after 
concentration and cooling deposits large, colorless tables of an- 
hydrous silver nitrate. If silver coin be employed, the solution 
will be blue, containing, independently of silver nitrate, cupric 
nitrate. The latter may be removed by evaporating the residue 
to dr3mess and carefully heating it, so that the salt may remain 
fused for some time. The cupric nitrate is decomposed, while 
the silver nitrate remains mixed with cupric oxide, from which 
it may be freed by solution and filtration. 

This salt dissolves in its own weight of cold, and in half 
its weight of boiling water. The solution is neutral to test- 
paper. When exposed to the air, it blackens, as do also the 
crystals and the fused salt, a partial reduction being produced 
by organic matters in the air. It blackens the skin from a 
similar cause. 



322 ELEMENTS OF MODERN CHEMISTRY. 

Hydrogen slowly reduces the solution of silver nitrate with 
deposition of metallic silver (Beketoff). 

Silver nitrate is extensively used in photography ; it is also 
used in medicine, and when fused constitutes lunar caustic. 

Characters of Silver Salts. — Solutions of silver are precipi- 
tated black by hydrogen sulphide and by ammonium sulphide. 

Caustic alkalies give an olive-green precipitate of silver 
oxide, insoluble in excess. Ammonia does not precipitate them. 

Hydrochloric acid and the soluble chlorides form a white 
precipitate of silver chloride, insoluble in either cold or boiling 
nitric acid, but soluble in ammonia. 

Potassium iodide gives a yellow precipitate, almost insoluble 
in ammonia. 

Silvering. — This operation consists in covering the common 
metals or glass with a coating of silver more or less thick. 

The metals are silvered by either amalgamation or galvanic 
deposition. In the latter and preferable operation, a solution 
of the double cyanide of silver and potassium is generally used. 

Mirrors and glass articles in general are silvered by the re- 
duction of a silver salt by aldehyde, glucose, or tartaric acid. 
The following receipt is given by Liebig: a solution of 10 
grammes of silver "nitrate is supersaturated with ammonia and 
rendered strongly alkaline by caustic soda. The volume of 
the liquid should be 1450 c.c. Another solution is prepared 
by dissolving 1 part of milk sugar in 10 parts of water. The 
latter solution is mixed with its own volume of the first solu- 
tion, and the glass to be silvered is washed with alcohol and 
immersed in the liquid. The reduction of the silver salt begins 
immediately, and does not require the aid of heat. 

The experiment may easily be made in a glass flask, the 
interior of which will be uniformly silvered. 

Assaying of Silver. — This name is applied to the methods 
which serve for the analysis of alloys of silver and copper, such 
as coin, medals, silverware, and jewelry. The assay may be 
conducted by the dry way or by the wet way. 

The dry assay consists in the operation called cupellation 
(Fig. 103). A certain quantity of metallic lead is melted in 
a cupel of bone-ash in a reverberatory furnace, and a weighed 
quantity of the alloy of silver and copper, carefully wrapped 
in a small piece of paper, is placed upon the fused metal. The 
silver dissolves in the melted lead, and a ternary alloy is thus 
obtained which is exposed to the action of air at a red heat. 



ASSAYING OF SILVER. 



323 



Under these conditions, the lead and copper become oxidized ; 
the oxide of lead fuses, and the melted litharge, which should 
be in great excess in proportion to the oxide of copper, dis- 
solves the latter, and with it is absorbed by the porous cupel. 
The phenomenon of brightening (page 346) indicates the ter- 
mination of the process. 




Fig. 103. 

The wet assay ^ invented by G-ay-Lussac, consists in. adding 
to a solution in nitric acid of a known weight of the alloy of 
silver and copper, a titrated solution of sodium chloride, that 
is, a solution containing an exactly known weight of salt in 
one litre of water. This solution is cautiously added until it 
no longer precipitates silver chloride, and the quantity of 
silver present is calculated from the volume of the titrated 
solution that has been required to completely precipitate the 
silver in the form of chloride. As the latter readily deposits 
from a liquid that is carefully agitated, it is easy to ascertain 
the end of the operation, that is, the precise moment when 
all of the silver is precipitated and the addition of the titrated 
liquid mast be arrested. 



324 ELEMENTS OF MODERN CHEMISTRY. 

Process. — Two titrated solutions are used to precipitate the 
silver : 1st, a normal solution, containing 0.5417 gramme of 
sodium chloride per decilitre, a quantity sufficient to precipitate 
one gramme of silver ; 2d, a decinorinal solution, that is, one 
containing the same quantity of sodium chloride per litre, so 
that 1 c.c. of this liquid will precipitate one milligramme 
of silver. To analyze an alloy of silver, a coin, for example, 
such a quantity is weighed as would contain one gramme of 
silver, if the proportion of silver were a little less than the 
extreme limit allowed. If the alloy ought to contain 900 
thousandths pure silver, with an allowance of 3 thousandths, it 
would be rejected should it contain less than 897 thousandths. 

We suppose, however, that the latter is its quality, and 
weigh a quantity of the alloy which would then contain one 
gramme of pure silver, that is, 1.1148 grammes. This alloy 
is dissolved in nitric acid, and one decilitre of the normal solu- 
tion is added. All of the silver should not be precipitated, for 
the standard of the alloy should be above 897. This is deter- 
mined by adding to the clarified liquid one or more cubic cen- 
timetres of the decinormal solution, until the liquid ceases to 
become cloudy on a fresh addition. As each cubic centimetre 
of this solution corresponds to one milligramme of silver, we 
must add to the gramme of silver at first precipitated as many 
milligrammes as we have added cubic centimetres of the deci- 
normal solution, the last cubic centimetre added counting for 
only half a milligramme. Knowing the quantity of pure silver 
contained in 1.1148 grammes of the alloy analyzed, the 
standard of the latter is determined by a simple calculation. 



CALCIUM. 

Ca = 39.8 

Lime, which is universally known, is the oxide of a metal 
called calcium. The latter was discovered by Davy in 1808, 
and isolated in 1854 by Matthiessen, who obtained it by 
decomposing fused calcium chloride by the voltaic current. 
According to Lies-Bodard and Jobin, calcium may be obtained 
by decomposing calcium iodide with sodium in an iron crucible. 

Calcium has a yellow color when freshly filed, but it tar- 
nishes rapidly in moist air and becomes covered with a grayish 



OXIDE AND HYDROXIDE OF CALCIUM. 325 

layer of hydroxide. When heated upon platinum-foil it takes 
fire and burns with a dazzling flame. It decomposes water at 
ordinary temperatures. 

OXIDE AND HYDROXIDE OF CALCIUM. 

Lime^ or calcium oxide^ CaO, is obtained by calcining the 
carbonate in special furnaces, which are called lime-kilns. As 
quick-lime, it forms large, compact, and hard grayish masses. 

It is infusible. When exposed to the air, it attracts moist- 
ure and carbonic acid, augments in volume, and is finally con- 
verted into a white powder, a mixture of calcium hydroxide 
and carbonate. When lime is sprinkled with water, it absorbs 
the liquid without giving rise to any particular phenomenon; 
but in a little while, the pieces saturated with water become 
hot, give ofi" steam, and then they split and increase in volume. 
If enough water be used, the quick-lime will be converted 
into a white powder, which is called slaked lime; it is calcium 
hydroxide. 

CaO -f WO = CaO^H'^ = Ca(0H)2 

When slaked lime is suspended in water, a white, creamy 
liquid is obtained that is called milk of lime. If this be fil- 
tered or allowed to settle, the clear, limpid liquid resulting will 
have an alkaline reaction, for it contains a small quantity of 
calcium hydroxide in solution : it is lime-iuater. Calcium 
hydroxide is more soluble in cold than in hot water. 

Employment of Lime in Constructions. — Lime is largely employed 
for building purposes in both ordinary and submarine constructions. 
The limestone which is used for the preparation of lime is rarely 
pure, and consequently the product of its calcination presents differ- 
ent qualities, according to the proportions of foreign matters which 
remain in the lime, and which consist of a small quantity of mag- 
nesia, oxide of iron, and especiallj^ clay. Fat limes are those pro- 
duced by the calcination of almost pure limestone ; they develop 
much heat, and swell up very much on slaking. Such lime forms 
an unctuous and binding paste with water, and makes ordinary 
mortar when mixed with sand. Impure limestones yield lean lime, 
containing magnesia, oxide of iron, and clay. It is gray, and de- 
velops but little heat and increases but slightly in volume on slaking. 
The calcination of limestone containing from 10 to 30 per cent, of 
clay produces hydraulic lime. Such lime sets under water, that is, 
the mortar solidifies after a few days, and becomes very hard, even 
when immersed in water. On account of this curious property it is 
used in submarine constructions. Such lime is yellow ; slaking it 
produces but little heat, and scarcely any increase in volume. The 

28 



326 ELEMENTS OF MODERN CHEMISTRY. 

hydraulic mortar formed by its mixture with sand will harden under 
water. Mortars possessing this property may also be prepared by 
mixing lime with baked argillaceous materials, such as powdered 
tiles, pottery, bricks, etc. Certain argillaceous rocks of volcanic 
origin, the pozzolana so abundant near Vesuvius, for example, yield 
an excellent hydraulic lime when mixed with fat lime. 

Cement is a variety of lime resulting from the calcination of lime- 
stones containing from 40 to 50 .per cent, of slate. When mixed 
with water, such cement sets in a few minutes in a solid mass like 
plaster. Vicat has shown that the diiferent varieties of hydraulic 
lime and cement can be prepared by properly calcining carbonate 
of lime, or chalk, with various proportions of clay. According to 
him, ordinary mortar sets because the lime gradually absorbs car- 
bonic acid gas from the air, forming a carbonate which hardens and 
binds together the grains of sand. The hardening of hydraulic 
lime and mortar is due to another cause : on contact with water, the 
clay which they contain in the anhydrous state becomes hydrated 
and forms a double silicate of calcium and aluminium, or a silicate 
and aluminate of calcium, which are insoluble and very coherent. 

CALCIUM CHLORIDE. 

CaCP 

This salt is prepared by dissolving white marble or chalk in 
hydrochloric acid. On evaporation, the solution deposits large, 
six-sided prisms, containing 6 molecules of water of crystal- 
lization. They are very deliquescent and lower the tempera- 
ture when they are dissolved in water. If they be mixed with 
their own weight of snow, a cold of — 45° may be produced. 
When they are heated, they melt in their water of crystal- 
lization, of which they lose 4 molecules at 200°, and the re- 
mainder at a red heat. At the latter point the mass enters 
into igneous fusion, and on cooling solidifies to a white, crys- 
talline mass, in which form it is ordinarily employed for the 
desiccation of gases. Calcium chloride dissolves readily in 
alcohol. 

CALCIUM CARBIDE. 
CaC2 

At the high temperature of the electrical furnace lime is 
promptly reduced by carbon, but metallic calcium is not ob- 
tained. The reduced metal combines with part of the carbon, 
forming a black, homogeneous, crystalline mass, which is the 
carbide CaC^ (H. Moissan). It has a density of 2.2, and is 
fusible at the high temperature at which it is formed. When 
heated in air, it burns into calcium carbonate. Water in- 
stantly reacts with it, forming calcium hydroxide and acety- 
lene, Qm\ 



CALCIUM NITRATE — CALCIUM CARBONATE. 327 

CALCIUM NITRATE. 

Ca(N03)2 + 4H20 

This salt is formed naturally in the neighborhood of dwell- 
ings, in the soils of cellars, and in damp walls. It is con- 
tained in what are known as saltpetre materials, and exists in 
certain spring and well waters. It may be made by satu- 
rating nitric acid with calcium carbonate. It is very soluble 
in water and in alcohol. It crystallizes with difficulty in six- 
sided, oblique rhombic prisms, which contain 4 molecules of 
water of crystallization : they are deliquescent. 

CALCIUM CARBONATE. 

CaC03 

Calcium carbonate, commonly known as carbonate of lime, 
is found in great abundance in nature and under different 
forms. It is dimorphous, being found as calcite crystallized 
in rhombohedra and as arragonite in right rhombic prisms. 
Iceland spar is calcite which is colorless and perfectly trans- 
parent ; the crystals are doubly refracting. 

The various limestones and marbles constitute natural cal- 
cium carbonate in which crystalline structure is more or less 
apparent, and many varieties are colored by foreign matters. 
All the varieties of marble are susceptible of a high polish. 
Statuary marhle is the whitest, and is made up of brilliant 
crystalline grains ; lithographic-stone is exceedingly fine- 
grained, very compact, and has a yellowish-white color. 

Chalk is a soft and amorphous calcium carbonate, made 
up of the mineral remains of marine animalcules. 

Pure water dissolves but feeble traces of this salt ; water 
charged with carbonic acid dissolves a larger quantity, con- 
verting it into dicarbonate. It is in this state that it is 
contained in hard waters. When the carbonic acid slowly 
evaporates, the calcium carbonate is deposited from such 
waters in compact form having crystalline structure, and 
when the water drips from the dome of a cave, large and 
fantastically shaped stalactites and stalagmites are frequently 
formed, consisting of almost pure calcium carbonate. 

Calcium carbonate may be prepared by double decomposi- 
tion between solutions of sodium carbonate and calcium 
chloride. When heated to bright redness, it is completely 
decomposed into lime and carbonic anhydride, 



328 ELEMENTS OF MODERN CHEMISTRY. 

CALCIUM SULPHATE. 

CaSO* 

This salt exists in two states in nature : anhydrous, it con- 
stitutes the anhydrite of mineralogists ; combined with two 
molecules of water of crystallization, it forms gypsum or plas- 
ter stone. G-ypsum sometimes occurs in lance-head-shaped 
crystals, grouped together ; they are divisible into thin, trans- 
parent layers, easily scratched by the finger-nail. Alabaster 
and satin-spar are varieties of gypsum. All the forms of 
hydrated calcium sulphate contain 21 per cent, of water. 

When heated to 80° in the air, or to 115° in closed vessels, 
the sulphate, CaSO* -|- 2H^0, abandons its water of crystalli- 
zation and is converted into the anhydrous sulphate. Between 
120 and 130°, this dehydration is rapid and complete. It is 
operated on the large scale in plaster furnaces. In this state 
calcium sulphate will readily recombine with its water of 
crystallization. If the plaster be calcined at too high a tem- 
perature it will not again become hydrated. 

If powdered plaster of Paris be mixed with enough water 
to form a creamy liquid, it may be poured into a mould, and 
in a few minutes will harden to a compact mass, completely 
filling every cavity of the mould. In becoming hydrated, the 
particles of calcium sulphate assume the crystalline form and 
increase in volume. These properties render plaster of Paris 
valuable in building operations, for ornamental work, and for 
making casts. 

It is also employed to a large extent in agriculture. 

Calcium sulphate is but slightly soluble in water. 1000 
parts of boiling water dissolve a little more than 2 parts of 
the salt; at 35° they dissolve 2.64 parts; at 20°, 2.05 parts. 



CHLORINATED LIME. 

(bleaching-powder.) 

This substance is largely employed in the arts under the 
name chloride of lime^ and is obtained by exposing well-slaked 
lime to the action of chlorine. Its constitution is not perfectly 
understood; it was long regarded as a mixture of calciunj 



CHLORINATED LIME. 



329 



chloride and calcium hypochlorite, CaCP + Ca(ClO)^ but re- 
cent researches have shown that it does not contain calcium 
hypochlorite already formed. 

The formation of the alkaline hypochlorites by the action of 
chlorine on a solution of an alkaline hydrate is explained on 
page 133. With the hydrates of diatomic metals like calcium 
the action is more complicated, and is probably expressed by 
the equation 

Ca(0H)2 -I- CP = Ca(OCl)Cl + H^O 

Its manufacture is conducted by passing a current of chlorine 
over slaked lime placed in layers upon shelves arranged in the 
walls of masonry chambers (Fig. 104). The product always 
contains a certain proportion of lime which cannot possibly be 
chlorinated. 




Fig. 104. 

Chlorinated lime is an energetic bleaching agent ; under the 
influence of acids it is decomposed, chlorine being set free. A 
solution of the compound is decomposed by the more feeble 
acids, even by carbonic acid gas, and decomposes spontaneously 
in a short time into calcium chloride and calcium hypochlorite. 

2a* 



330 ELEMENTS OF MODERN CHEMISTRY. 

Inasmuch as the substance is a mixture, and not a definite 
compound, its reactions may be interpreted in several different 
manners. It always contains water, calcium hydroxide, and a 
proportion of calcium chloride, and its active principle is 
probably expressed by one, or perhaps both, of the following 
formulae : 

Ca<^^^ = CaOCP ; ^^<0E =" ^^^^^-^^ 

The reactions might then be written as follows: 
The spontaneous decomposition of the solution, 

2CaOCP = Ca(ClO)^ -f CaCP 

Calcium hypochlorite. Calcium chloride. 

2CaOC1.0H = Ca(ClO)^ + Ca(0H)2 ; 

its decomposition by hydrochloric acid, 

CaOCP + 2HC1 = CaCP + H^O + CP 

CaOClOH + 3HC1 = CaCP + 2H20 + CP 

When a solution of chlorinated lime is boiled, it is at once 
decomposed, yielding calcium chloride and calcium chlorate : 

eCaOCP = 5CaCP + Ca(C10^)2 

Calcium chloride. Calcium chlorate. 

Characters of Calcium Salts. — Calcium salts are not pre- 
cipitated either by hydrogen sulphide or ammonium sulphide. 
Sodium carbonate forms in them a white gelatinous precipitate. 
Sulphuric acid and the soluble sulphates produce a white pre- 
cipitate, if the calcium solutions be concentrated or only mod- 
erately dilute. Oxalic acid, or better, ammonium oxalate, 
produces a white precipitate of calcium oxalate, even in the 
most dilute solutions of calcium salts. Calcium compounds 
impart an orange-red color to non-luminous flames. 



STRONTIUM. 

Sr = 86.95 

Strontium was discovered by Davy in 1808, but the pure 
metal was first obtained by Bunsen and Matthiessen by a pro- 
Qes3 similar to that which serves for the preparation of barium, 



BARIUM. 331 

Matthiessen describes it as a yellow metal, having a density 
of 2.50-2.58, harder than lead, and decomposing cold water. 

Strontium forms two oxides, a monoxide^ SrO, and a dioxide^ 
SrOl 

Strontium chloride, SrCP, crystallizes in deliquescent needles 
which contain six molecules of water of crystallization. It 
is very soluble in water and fairly soluble in alcohol; the 
alcoholic solution burns with a red flame. 

Strontium nitrate, Sr(NO^)^, which is prepared like barium 
nitrate, is deposited from its hot aqueous solution in anhydrous 
octahedra, and crystallizes at low temperatures in oblique rhom- 
bic tables containing 5 molecules of water of crystallization 
(Laurent). 

The carbonate of strontium, SrCO' (strontianite^, and the 
sulphate, SrSO* (celestite), are found native. These two salts 
are insoluble in water, and are deposited as white precipitates 
on adding a soluble carbonate or sulphate to the solution of a 
strontium salt. Strontium sulphate is less insoluble, however, 
than barium sulphate. Strontium salts color flames red, and 
the nitrate is used in red fire. 



BARIUM. 

Ba = 136.4 

Bunsen obtained barium by the electrolysis of fused barium 
chloride ; this metal is very avid of oxygen, and tarnishes 
rapidly. It decomposes cold water. 

Barium Oxide, or Baryta, BaO. — Barium oxide is obtained 
by calcining barium nitrate. Its nature was first recognized 
in 1808, by Davy, who decomposed it by the voltaic current. 
It is a gray, porous substance, which unites energetically with 
water, producing a hissing noise and a great disengagement of 
steam, due to the elevation of temperature. The product of 
the reaction is a white hydrate, ordinarily known as caustic 
baryta. 

BaO + WO = Ba(0H)2 

Barium oxide. Barium hydroxide. 

Barium hydroxide is soluble in two parts of boiling water, 
and on cooling is in great part deposited in large tabular crys- 
tals, containing 8 molecules of water. The solution of barium 
hydroxide in water is called baryta water, 



332 ELEMENTS OF MODERN CHEMISTRY. 

Barium Dioxide, BaO^ — When dry oxygen is passed over 
barium oxide heated to dull redness, the gas is absorbed and a 
dioxide, BaO^ is formed. It is a gray, porous mass, some- 
times greenish. It loses one atom of oxygen at a bright-red 
heat (see page 66). When brought in contact with water, it 
combines with the latter quietly and without disengagement of 
heat, forming a pulverulent hydrate. 

This hydroxide is readily prepared pure by adding an 
excess of baryta water to a solution of hydrogen dioxide ; it 
separates in beautiful scales. It reacts with cold dilute hydro- 
chloric acid, forming barium chloride and hydrogen dioxide. 

Barium Sulphide, BaS. — This is obtained by reducing 
barium sulphate with charcoal. 

BaSO* + C* = BaS + 4C0 
The sulphate is reduced to fine powder, and is mixed with a 
certain quantity of flour or rosin. The mixture is then made 
into a paste with linseed oil, and shaped into little balls. These 
are calcined at a bright-red heat in a covered crucible, and a 
porous, gray mass is thus obtained which, when treated with 
boiling water, yields a solution which deposits hexagonal tables 
after filtration and cooling. These crystals do not present a 
very constant composition, being a mixture of sulphide, hydro- 
sulphide, and hydroxide of barium. Their solution has a light- 
yellow color. 

BARIUM SALTS. 

Barium Chloride, BaCP + 2H'0.— This salt is obtained 
by saturating the solution of barium sulphide with hydrochloric 
acid. Hydrogen sulphide is disengaged ; the solution is boiled, 
filtered, and evaporated to crystallization. Barium chloride 
separates in quadrangular tables belonging to the type of the 
right rhombic prism. These crystals are inalterable in the air. 
100 parts of water at 18° dissolve 43.5 parts of barium chlo- 
ride, and 78 parts at 105.5°, the temperature of ebullition of 
the saturated solution (Gray-Lussac). Absolute alcohol dis- 
solves -jl-Q- of its weight of barium chloride. 

Barium Nitrate, Ba(NO^)^ — Barium nitrate is prepared 
by decomposing barium sulphide or carbonate with dilute nitric 
acid, and filtering and evaporating the solution. 

It crystallizes in regular octahedra, or in cubo-octahedra. 
The crystals are transparent and unaltered in the air. One 



GLUCINUM, OR BERYLLIUM. 333 

part of this salt requires for its solution 20 parts of water at 
0.12° ; 5 parts of water at 15° ; 2.8 parts at 106°, the tem- 
perature of ebullition (Gay-Lussac). When heated to redness, 
barium nitrate gives off oxygen, nitrogen, and red vapors, leav- 
ing a residue of oxide, BaO. 

Barium Sulphate, BaSO*. — This salt is found abundantly 
in nature as lieavy spar, and sometimes occurs in right rhom- 
bic crystals. It is entirely insoluble in water and acids, with 
the exception of concentrated sulphuric acid. It is precipi- 
tated as a finely-divided, amorphous powder when sulphuric 
acid or a soluble sulphate is added to a solution, even very di- 
lute, of a salt of barium. 

Barium Carbonate, BaCO^. — Barium carbonate constitutes 
an amorphous, white powder, which is obtained by double de- 
composition on adding solution of sodium carbonate to a solu- 
tion of barium sulphide. Natural barium carbonate is an 
abundant mineral, and is found crystallized in right rhombic 
prisms; it is called loitlierite. 

Characters of Barium Salts. — Barium salts are precipi- 
tated neither by hydrogen sulphide nor by ammonium sulphide. 
Sodium carbonate produces in them a white precipitate. Even 
when very dilute, the barium salts produce a white precipitate 
with sulphuric acid, which is insoluble in either cold or boiling 
nitric acid. The salts of barium communicate a green color to 
flames ; the nitrate is used in green fire. 



Grlucinum, magnesium, zinc, and cadmium form a group in 
which the chemical analogies of the members are well marked. 
They are diatomic, forming oxides BO, and chlorides RCP. 

GLUCINUM OR BERYLLIUM. 

Gl, or Be = 9.01 

The varieties of beryl, including the green precious stone 
emerald and aqua-marine, contain a double silicate of aluminium 
and glucinum. The latter metal was first isolated by Woehler 
in 1827. 

Glucinum is prepared by the reduction of its chloride by po- 
tassium or sodium. It is white and brilliant, has a density of 
1.6, and melts at a temperature below the fusing-point of silver. 
It does not decompose water, even by the aid of heat, but is 



334 ELEMENTS OF MODERN CHEMISTRY. 

readily attacked by hydrochloric and sulphuric acids, hydrogen 
being evolved and a chloride or sulphate formed. 

Glucinum Oxide, GIO, is prepared from beryl, or by pre- 
cipitating by ammonia a solution of glucinum chloride. In the 
latter case a hydrate Gl(OH)^ is obtained, which is converted 
into oxide by heat. 

The oxide is a light, white, infusible powder, soluble in acids 
and alkalies. When heated in the oxyhydrogen flame, it vola- 
tilizes like magnesium and zinc oxides. 

Glucinum Chloride, GICP. — This salt may be prepared by 
passing chlorine over an intimate mixture of the oxide and 
charcoal at a high temperature. 

Glucinum chloride forms white, deliquescent crystals that 
fume in the air, condensing atmospheric moisture. It is fusible, 
and volatilizes at a low red heat. It is very soluble in water, 
and forms a hydrate which is decomposed by heat, yielding 
glucinum oxide and hydrochloric acid. 

Glucinum forms a nitrate, and a sulphate which is isomor- 
phous with magnesium sulphate. 

The salts of glucinum possess a sweet taste, to which the 
metal owes its name. 



MAGNESIUM. 

Mg = 24.18 

Magnesium was discovered by Bussy. Matthiessen obtained 
it by decomposing fused magnesium chloride by electricity. 

Preparation. — Deville and Caron recommend the following 
process for the preparation of considerable quantities of mag- 
nesium. A mixture of 600 grammes of anhydrous magnesium 
chloride, 100 grammes of sodium chloride, 100 grammes of 
calcium fluoride, and 100 grammes of sodium cut into small 
pieces is heated to redness in a covered crucible. The mag- 
nesium chloride is reduced by the sodium, and the magnesium 
set free collects in little globules disseminated in the fused 
mass, which must be stirred with an iron rod. These little 
globules are removed from the scoriae when cold, introduced 
into a charcoal boat, and heated to bright redness in a cur- 
rent of hydrogen. The magnesium volatilizes and condenses 
farther on in the tube ; it may then be fused with a flux con- 
sisting of magnesium chloride, sodium chloride, and calcium 
fluoride. The metal collects at the bottom of the crucible. 




MAGNESIUM OXIDE, OR MAGNESIA. 335 

Within recent years magnesium lias acquired considerable 
commercial importance. It is manufactured by electrolyzing 
carnallite, the double chloride of magnesium and potassium. 
This salt is fused in an iron crucible (A, Fig. 105), which 
serves as a negative electrode. A carbon rod forms the 
anode, which is enclosed 
by a porcelain cylinder 
perforated at the bottom to 
permit free passage of the 
fused carnallite, and con- 
nected at the top with a 
pipe to carry off the evolved 
chlorine. In this manner 
the metal liberated at the 
cathode cannot come in [ T ^ _ 7 

contact with the chlorine, Pjq 1Q5 

with which it would at 

once recombine, and it is protected from oxidation by the 
passage of an inert gas, such as nitrogen or hydrogen, through 
the space in the iron retort. 

Properties. — Magnesium has a density of 1.74 or 1.75. It 
fases at 500°. It decomposes water at ordinary temperatures 
but slowly. It may readily be rolled into ribbon or drawn into 
wire. The wire is grayish and not very brilliant. The end 
of a bundle of these wires may be heated in an alcohol lamp 
until they take fire, and the whole may then be plunged into a 
jar of oxygen. They burn with an incomparable splendor that 
the eye cannot support; at the same time the jar becomes filled 
with a white smoke, which condenses into a white powder, the 
product of the combustion ; it is magnesia, the oxide of mag- 
nesium. Magnesium also combines directly with nitrogen. 

In the form of powder, magnesium is employed in the 
flash-lights used in photography and in pyrotechnics. 

MAGNESIUM OXIDE, OH MAGNESIA. 
MgO 
This body is obtained by calcining white magnesia, or mag- 
nesium hydrocarbonate. It is a white, voluminous powder, 
less fusible even than lime. It does not dissolve in water, 
but combines with that liquid forming a hydrate, Mg(OH)''* 
= MgO.H^O. This hydrate slowly restores the blue color 
to reddened litmus-paper. 



336 ELEMENTS OF MODERN CHEMISTRY. 

Magnesium hydroxide is precipitated when a solution of 
caustic potash is added to the solution of a magnesium salt. 

Calcined magnesia is frequently employed in medicine. 
On account of its great infusibility (it melts only at the 
temperature of the electric arc), crude magnesia is employed 
for lining furnaces and crucibles. 

MAGNESIUM CHLORIDE. 

MgCP 

This salt is known in the anhydrous state and crystallized. 
Anhydrous magnesium chloride is prepared by dissolving the 
carbonate in hydrochloric acid, adding ammonium chloride to 
the solution and evaporating to dryness. A double chloride of 
magnesium and ammonium is thus obtained which may be per- 
fectly dried ; the dry mass is introduced into a clay crucible and 
heated ; the ammonium chloride volatilizes, while the magne- 
sium chloride remains, and solidifies on cooling to a colorless, 
pearly mass. 

It is very soluble in water, and when properly concentrated, 
the solution deposits deliquescent, prismatic crystals containing 
six molecules of water of crystallization. These crystals can- 
not be dehydrated, nor can their solution be evaporated to 
dryness, without decomposing the chloride by the action of the 
water; under these circumstances the magnesium chloride is 
converted into hydrochloric acid and magnesia. 

MgCP + H^O = 2HC1 + MgO 

MAGINESIUM CARBONATE. 

MgCO^ 

The anhydrous carbonate MgCO^, known as magnesite, is 
found native, crystallized in rhombohedra, similar to those of 
calcium carbonate. Considerable deposits are also found of a 
double carbonate of magnesium and calcium, known as dolomite. 

When a boiling solution of magnesium sulphate is precipi- 
tated by an excess of sodium carbonate, carbonic acid gas is 
disengaged, and a precipitate is formed containing at the same 
time magnesium carbonate and magnesium hydrate (magnesium 
hydrocarbonate). 

When this is dried, it constitutes the white magnesia of the 
pharmacies. 



ZINC. 337 

MAGNESIUM SULPHATE. 

MgSO* + 7H20 

This salt exists in solution in sea-water and in certain pur- 
gative mineral waters, such as those of Epsom, in England. 
Its common name is Epsom salts. 

At Stassfurt, it is found crystallized with one molecule of 
water (Ideserite) and mixed with the anhydrous sulphate. 

When it separates at ordinary temperatures from an aqueous 
solution that has been tolerably concentrated by heat, it crystal- 
lizes in transparent and colorless right rhombic prisms. At 0°, it 
crystallizes with 12 molecules of water ; at 30°, with 6 molecules. 
Its taste is disagreeable, at the same time salty and bitter. When 
magnesium sulphate crystallized with 7 molecules of water is 
heated, it first melts in its water of crystallization, of which it 
loses 6 molecules. At 132°, it still retains one molecule, which 
it loses only at 210°. It is very soluble in water ; 100 parts of 
water at 0° dissolve 25.76 parts of the anhydrous sulphate, and 
0.4781 6 part for every additional degree (Gay-Lussac). It forms a 
double sulphate with potassium sulphate, K^SO^MgSO^ -f GH^O. 

Characters of Magnesium Salts. — They are precipitated 
by neither hydrogen sulphide nor ammonium sulphide. Sodium, 
carbonate produces a white, flocculent precipitate. Caustic 
potash and ammonia form white precipitates, but ammonia 
will not precipitate magnesia from an acid solution or from one 
containing ammonium chloride. Sodium phosphate and ammonia 
together produce a crystalline precipitate of ammonio-magne- 
sium phosphate. This is the most delicate test for magnesium. 



ZINC. 

Zn = 64.91 

Treatment of Zinc Ores. — The most important ores of 
zinc are zinc spar (smifhsonife) , ZnCO* ; blende or sphalerite, 
ZnS; calamine, Zn^SiO' -f H^O ; willemite, Zn^SiO*; red 
zinc ore, ZnO, ?ind franJdimte, (Zn,Fe)O.Fe^O^ 

Zinc ores are abundant in England, Silesia, Belgium, and 
throughout the United States. They are generally accom- 
panied by other minerals ; thus, blende is often mixed with 
pyrites and galena (lead sulphide). The ore is then first 
submitted to an ingenious system of washing, by which the 
T w 2e. 



338 



ELEMENTS OF MODERN CHEMISTRY. 



various sulphides separate from eacli other by reason of their 
different densities. 

In order to extract the zinc from blende separated by this 
method, or from zinc spar, the minerals are first roasted. By 
the action of heat zinc spar loses carbonic acid gas and water, 
and the blende disengages sulphur dioxide and is converted 
into zinc oxide. Thus converted into oxide, and rendered more 
friable by the heat, the zinc ores are pulverized and calcined 
with charcoal. Carbon monoxide is disengaged, and the zinc 
set at liberty volatilizes, and is condensed in suitable receivers. 

The operation is conducted in cylinders of refractory clay, 
a number of which are arranged in a furnace, and their open 
extremities connected with conical recipients of galvanized 
iron (Fig. 106). In Silesia, these cylindrical retorts are re- 
placed by muffles, which are heated in a furnace and com- 
municate with recipients placed outside (Fig. 107). 




Fig. 106. 



Fig. 107. 



The zinc of commerce is impure. It contains small quan- 
tities of iron, copper, lead, cadmium, carbon, and arsenic. 
It may be purified by repeated meltings with small quantities 
of nitre. The last traces of impurities can be removed only 
by fractional distillation in vacuo (Morse). 

Properties. — Zinc has a bluish-white color ; its density 
varies from 6.86 to 7.2, according as it has been melted or 
rolled ; its fracture is laminated and brilliant. Commercial 



ZINC OXIDE. 339 

zinc is brittle at ordinary temperatures ; it becomes malleable 
at a few degrees above 100°, but when heated to 200° it 
again becomes brittle. It melts at 410°, and distils at about 
1000°. Its vapor density compared to hydrogen indicates 
that the molecule contains but one atom. Its surface soon 
tarnishes in moist air, but the tarnish is only superficial. It 
is due to the formation of an impermeable layer of hydro- 
carbonate of zinc, which protects the metal from further 
oxidation. 

When heated to redness in air, zinc volatilizes and burns 
with a greenish flame into a smoke of oxide, which falls in 
light, white flakes, formerly called flowers of zinc or philoso- 
pher's wool. 

Zinc dissolves with evolution of hydrogen in hydrochloric 
and sulphuric acids, and in boiling solutions of potassium and 
sodium hydroxides. When perfectly pure, it is dissolved with 
difficulty by dilute sulphuric acid at ordinary temperatures, and 
the easy solubility of the metal of commerce must be attrib- 
uted to the presence of small quantities of foreign metals. The 
latter being electro-negative in contact with zinc, form voltaic 
couples, in which the zinc is the more oxidizable metal. 

Galvanized iron is iron covered with a thin layer of zinc ; it 
is prepared by plunging carefully-cleaned iron objects into a 
bath of molten zinc. 

Brass is an alloy of copper and zinc, obtained by melting the 
two metals together in crucibles. 

ZINC OXIDE. 

ZnO 

This oxide is prepared in the arts by heating zinc in large 
muffles ; the product is separated from traces of metallic zinc 
by suspending it in water and rapidly decanting the white 
liquid. The zinc sinks to the bottom of the A^essel before the 
lighter white powder has time to deposit ; the latter is therefore 
carried by the water into a second vessel, where it is allowed 
to settle. The process is called elutriation. 

This oxide is now manufactured on an enormous scale by 
drawing an excess of air through a burning mixture of zinc ore 
and coal. The zinc is reduced and oxidized at one operation, 
and the oxide is drawn through the blower and collects in can- 
vas bags through which the waste gases are forced. 



340 ELEMENTS OF MODERN CHEMISTRY. 

Oxide of zinc is white ; it turns yellow wlien heated, is 
infusible and is irreducible by beat and insoluble in water. 
The corresponding hydroxide is precipitated when caustic 
alkalies are added to the solution of a zinc salt, 

ZnSO^ + 2K0H = K^SO* + Zn(OHy 

Zinc sulphate. Zinc hydroxide. 

An excess of alkali will redissolve the precipitate. 
Zinc oxide is largely used in the arts as a substitute for 
white lead as a pigment. 

ZINC SULPHIDE. 

ZnS 

The blende which occurs in nature is sulphide of zinc. It 
crystallizes in the isometric system, often in hemihedral forms. 
Sometimes it occurs as lourtzite in hexagonal prisms (Friedel). 

On adding an alkaline sulphide to a neutral solution of a 
zinc salt a white precipitate is obtained, which is hydrated zinc 
sulphide. This precipitate is soluble in mineral acids. 

When moderately heated in contact with the air, zinc sul- 
phide absorbs four atoms of oxygen and is converted into sul- 
phate. At a very high temperature it is converted into oxide, 
with formation of sulphurous oxide. 

ZINC CHLORIDE. 

ZnC12 

Zinc reduced to thin sheets will burn in chlorine. Zinc 
chloride is prepared in the laboratory by dissolving zinc in 
hydrochloric acid. The aqueous solution, evaporated to a 
syrupy consistence, deposits a hydrated chloride, ZnCP -|- H^O, 
crystallizing in deliquescent octahedra. This salt loses its 
water when strongly heated, and melts at about 250°. On 
cooling, a solid white mass is obtained, which is the anhydrous 
chloride ; in this state it is very avid of water and deliquesces 
when exposed to the air. It volatilizes without decomposition 
at a red heat. It is very soluble in water, and dissolves also 
in alcohol. 

ZINC SULPHATE. 

ZnSO^ + 7H20 

This salt was formerly known as white vitriol. It is ob- 
tained by moderately roasting blende. The latter being often 



CHARACTERS OP ZINC SALTS. 341 

mixed with pyrites, zinc sulphate and ferrous sulphate are 
formed, and when the product of the roasting is lixiviated a 
solution of the two salts is obtained. The solution is evapo- 
rated, and the dry residue moderately calcined. The ferrous 
sulphate decomposes, yielding sulphuric acid, which distils, and 
ferric oxide, which remains mixed with the zinc sulphate. The 
residue being exhausted with water, the zinc sulphate dissolves 
and is deposited in crystals on the cooling of the concentrated 
solution. 

The salt may be prepared in the laboratory by dissolving 
zinc in dilute sulphuric acid : it is the residue in the prepara- 
tion of hydrogen. 

Sulphate of zinc crystallizes with 7 molecules of water. In 
this state it occurs as orthorhombic prisms, isomorphous with 
magnesium sulphate. 

When heated, it melts in its water of crystallization, of 
which it loses 6 molecules ; the seventh it abandons only at 
238°. 

At a high red heat it is decomposed into zinc oxide, sul- 
phurous oxide, and oxygen. 

Zinc sulphate is very soluble in water, of which 100 parts 
dissolve 48.36 parts of the anhydrous salt at 10°, and 95.6 
parts at 100°. The solution has a styptic taste. 

Zinc sulphate forms crystallizable double salts with the alka- 
line sulphates ; thus, there is a double sulphate of zinc and 
potassium, containing 

ZnSOMPSO* + QWO 

Characters of Zinc Salts. — The zinc salts are colorless 
unless the corresponding acid be colored. Their neutral solu- 
tions are partially decomposed by hydrogen sulphide, which 
precipitates white sulphide of zinc ; the addition of a mineral 
acid prevents the precipitation ; the zinc salts of organic acids, 
such as the acetate and lactate, are completely decomposed by 
hydrogen sulphide. 

Ammonium sulphide produces a white precipitate of sul- 
phide; this reaction is characteristic. 

The alkaline hydroxides, and ammonia-water, form white 
precipitates, soluble in an excess of the reagent. 

Potassium ferrocyanide gives a white precipitate. 



29* 



342 ELEMENTS OF MODERN CHEMISTRY. 

CADMIUM. 

Cd = 111.08 

Natural State arid Extraction. — Cadmium is generally 
found associated with zinc, either as oxide in calamine, or as 
sulphide in zinc blende. As it is more volatile than zinc, it 
becomes concentrated in the first products of distillation. 

It is found especially, in the state of oxide, in the brown 
powder called cadmies^ which condenses during the first hours 
of the distillation in the sheet-iron receivers adapted to the re- 
torts (Fig. 106). When mixed with powdered charcoal and 
calcined, this powder yields an alloy of zinc and cadmium 
which distils. 

The cadmium is extracted by dissolving the alloy in dilute 
sulphuric acid and passing a current of hydrogen sulphide 
through the acid liquid. The cadmium is precipitated as a 
yellow sulphide. This sulphide is dissolved in hydrochloric 
acid and the solution of cadmium chloride precipitated by am- 
monium carbonate. The cadmium carbonate thus obtained is 
calcined, and so converted into oxide, which is mixed with 
one-tenth its weight of powdered charcoal and heated in a clay 
retort. The cadmium distils. 

Properties. — Pure cadmium has a white lustre, but soon 
tarnishes in the air. Its density is 8.60-8.69. It melts at 
320°, and boils at 860°. Its vapor density is 56. It may 
be obtained crystallized in octahedra. 

It dissolves in dilute sulphuric and hydrochloric acids with 
evolution of hydrogen. 

Cadmium Oxide, CdO. — The oxide of cadmium may be ob- 
tained by calcining either the carbonate or nitrate. It has a 
yellowish-brown color, or a brown more or less deep. It is re- 
duced at high temperatures by carbon and by hydrogen, its 
reduction taking place more readily than that of zinc oxide. 

Cadmium Sulphide, CdS. — This sulphide occurs in nature 
as greenockite in the form of bright yellow, hexagonal prisms, 
terminated by six-sided pyramids. 

It may be prepared in the laboratory by precipitating a solu- 
tion of a cadmium salt by hydrogen sulphide or a soluble sul- 
phide. An amorphous precipitate of a fine yellow color is thus 
obtained. In this form it is employed in oil painting. 

Cadmium Iodide, CdP. — This salt is prepared, by digesting 



LEAD. 343 

finely-divided cadmium with iodine in presence of water. It 
crystallizes from its aqueous solution in transparent and color- 
less, hexagonal prisms having a brilliant lustre. It is soluble 
in water and alcohol. 

Cadmium Sulphate, 3CdS0* + 8H='0.— Cadmium Sul- 
phate is obtained by dissolving the metal, or its oxide or 
carbonate, in dilute sulphuric acid. The neutral and con- 
centrated solution deposits the salt in beautiful monoclinic 
prisms. These crystals are efflorescent. 



LEAD. 

Pb (Plumbum) = 205.4. 

Lead is related to the diatomic metals by a series of normal 
salts, the chloride PbCP, sulphide PbS, oxide PbO, etc., but 
it is undoubtedly tetratomic in other compounds, among which 
are a tetrachloride PbCl*, and a dioxide PbO^ It is probable, 
however, that lead is tetratomic in all of its compounds, in 
which case the dichloride must be represented by the formula 

C{>Pb=Pb<C| 

the oxide by the formula OPb=PbO, and the other compounds 
in an analogous manner. It is convenient, in the absence of 
more positive data, to represent these molecules by the more 
simple formulae, bearing in mind that they probably express 
only half the molecular weights. 

Treatment of Lead Ores. — The minerals of lead which are 
Worked are the carbonate, and especially the sulphide, known as 
galena. 

The extraction of the metal from the carbonate is simple : 
it is heated with charcoal in a cupola-furnace, and the reduced 
lead collects on the hearth. 

Two methods are employed for the reduction of galena. 
One consists in melting the ore with iron (granulated cast iron). 
Sulphide of iron is formed, and both it and the reduced lead 
enter into fusion and separate from each other by virtue of 
their different densities, the lead being much the heavier. 
This is the precipitation method. It is employed for impure 
ores having a silicious gangue. 

By the other process, known as the reaction method^ the 



344 



ELEMENTS OP MODERN CHEMISTRY. 



galena is first roasted, by wliich the sulphide is partially trans- 
formed into oxide and sulphate ; the openings of the furnace 
are now closed and the temperature is elevated. The excess 
of sulphide then reacts upon the oxide and upon the sulphate ; 
sulphurous acid gas is disengaged, and metallic lead is formed. 
This is called work-lead. 

PbS + 2PbO = 3Pb + SO^ 

PbS + PbSO* = 2Pb + 2S0^ 

The operation is conducted in a reverberatory furnace repre- 
sented in Fig. 108. The ore is spread in thin layers on the 




$$$5$$§§^$^:§$$$;;$$^$$\\^^^ 



Fig. 108. 



hearth E, and heated to dull redness ; the fire is at A, and the 
air enters by the openings D. These are closed when it is 
judged by the aspect of the mass that the roasting is suffi- 
ciently advanced. The heat is then increased. 

Independently of the portion of lead sulphide which reacts 
upon the oxide and sulphate, there is always an excess, which 
melts when the heat is increased, and separates in the form of 
lead matte. This is subjected to another operation by the same 
process of reaction, and furnishes a harder lead than that first 
obtained ; it contains a small quantity of copper, and is known 
as slag lead. 

In some works, charcoal-powder is added at a certain stage 
of the roasting, to remove the oxygen from the oxide and sul- 
phate formed. 



LEAD. 



345 



Treatment of Argentiferous Lead. — The lead produced by 
these metliods, and especially the work-lead, often contains a 
small proportion of silver. In order to separate the latter 
metal, the lead is desilverized, as described on page 317, or 
is first refined by crystallization. 

The object of refining hy crystallization is the formation of 
an alloy of lead and silver, richer in silver than the work-lead. 
The argentiferous lead is melted and allowed to cool slowly; 
nearly pure lead separates in the form of crystals, which are 
deposited at the bottom of the molten metal. These are re- 
moved by a ladle as fast as they are formed ; the richer alloy 




Fig. 109. 

of lead and silver remains liquid. The crystals of lead still 
contain a little silver, and are submitted to another fusion ; lead 
again crystallizes out on cooling, and a small quantity of an 
alloy still rich in silver is obtained. The same operation re- 
peated a third time determines the separation of pure lead. 
The alloys of lead and silver thus obtained are themselves sub- 
mitted to several successive fusions and crystallizations, and a 
still richer alloy results. 

The alloy thus concentrated is cupelled. The operation con- 
sists in melting the lead in' a reverberatory furnace (Fig. 109), 



346 ELEMENTS OF MODERN CHEMISTRY. 

of which the hearth has a hemispherical form, and is called 
the cupel. The vault of the furnace is formed by a sheet-iron 
cover, Gr, which can be raised and lowered at will. When the 
lead is melted, a strong blast of air is blown upon its surface 
through the tuyeres tt; the lead is thus converted into oxide, 
which melts and, driven by the current of air, flows from the 
cupel through a notch cut in its edge down to the level of the 
molten metal, and which is gradually deepened as that level 
becomes lowered. The silver, which is not oxidizable, becomes 
concentrated in the cupel as the lead is eliminated ; and when 
the last portions of the latter metal become oxidized, the sur- 
face of the silver is covered with only a thin layer of fused 
litharge, which breaks up suddenly and displays the brilliant 
surface of the metal. This phenomenon, called brightening^ 
indicates the termination of the operation. 

The oxide of lead formed first in the cupellation of work- 
lead is called ahstrich. It is black, and still contains a little 
silver, as well as copper and antimony (Berthier). The oxide 
which flows out after the abstrich is litharge. 

Properties of Lead. — Lead is a bluish-white metal, having 
a certain degree of lustre when its surface is freshly cut. It 
is the softest and least tenacious of all the common metals. It 
can easily be cut with a knife and scratched by the finger-nail. 
It may readily be reduced to thin sheets, but is not easily drawn 
into wire. Its density is 11.363 (H. Deville). It melts be- 
tween 326 and 334°, and volatilizes at a white heat. It may 
sometimes be obtained crystallized in regular octahedra by 
allowing a large quantity of molten lead to cool slowly, and 
decanting the still liquid portion. 

The brilliant surface of lead tarnishes in the air. When 
melted, it rapidly absorbs oxygen and becomes covered with a 
pellicle of oxide, which is transformed by the prolonged action 
of heat into a yellow powder, known as massicot. 

On contact with aerated water, lead absorbs oxygen and car- 
bon dioxide, and becomes covered with a thin layer of carbon- 
ate. This fact explains the presence of traces of lead in rain- 
water which has been collected from lead gutters, or kept in 
leaden reservoirs. 

The presence of small quantities of sulphates and chlorides 
in water prevents this oxidation of lead, so that the metal can 
be used without danger for the distribution of most spring and 
river waters, 



LEAD MONOXIDE. 347 

Lead is slowly attacked by concentrated and boiling bydro- 
cbloric acid. Dilute snlpburic acid does not attack it ; tbe 
boiling concentrated acid converts it into sulphate with evolu- 
tion of sulphurous acid gas. Xitric acid attacks and dissolves 
it at ordinary temperatures, disengaging red vapors and forming 
lead nitrate. 

Lead and its compounds are poisonous. Its effects on the 
economy are especially manifested after the long-continued 
absorption of very small quantities of the metal, of which the 
accumulation in the system is made evident by various symp- 
toms; the best known is lead colic qt painter' s colic. Plumbers, 
glaziers of pottery, painters, color-grinders, and the workmen 
employed in the manufacture of minium, or red lead, white 
lead, etc., are exposed to this chronic poisoning. The soluble 
sulphates are antidotes for acute cases of poisoning, and potas- 
sium iodide causes the elimination of lead from the system in 
chronic cases. 

Uses of Lead. — This metal is used for the manufacture of 
shot, and pipes for the distribution of water and gas. TThen 
reduced to sheets it is made into gutters, the coverings of roofs. 
linings for troughs and reservoirs. Sheet-iron dipped into a 
bath of melted lead retains a coating of that metal, and is called 
leaded iron. Lead enters into the composition of type-metal, 
plumber's solder, pewter, etc. 

LEAD 3I0X0Xn)E. 

PbO 

Massicot and litharge . of which the formation has been in- 
dicated, constitute the monoxide of lead. 

Massicot is a yellow, amorphous powder. Litharge occurs in 
reddish-yellow, crystalhne scales. It is rendered crystalline by 
the fasion and cooling through which it passes. It is sometimes 
met with in the form of rhombic octahedra (Mitscherlich). 

Oxide of lead melts at a red heat ; when fased it absorbs 
oxygen, which it again gives up on solidifying (F. Le Blanc). 

It cannot be melted in an earthen crucible without attacking 
and sometimes piercing the latter, owing to the formation of a 
very fasible silicate of lead. 

Lead monoxide is easily reduced by hydrogen, charcoal, and 
carbon monoxide. 

It is very slightly soluble in water, and possesses a suf&cientlj 



348 ELEMENTS OF MODERN CHEMISTRY. 

marked alkaline reaction to restore the blue color to feebly 
reddened litmus-paper. 

When caustic alkalies or ammonia-water are added to solu- 
tions of lead salts, white precipitates of lead hydroxide, 
Pb(OH)^ are produced. This hydroxide dissolves in an excess 
of potassium or sodium hydroxide, or in lime-water, and 
these solutions are precipitated black by hydrogen sulphide. 

Litharge is used for the manufacture of lead acetate and 
white lead. It gives to linseed oil drying properties. It enters 
into the composition of various plasters, and diiFerent coloring 
matters (Cassel yellow). 

LEAD DIOXIDE. 

Pb02 

This body is made by treating minium, or intermediate oxide 
of lead, with dilute nitric acid. A brown powder remains and 
must be washed with boiling water. This is dioxide of lead ; 
it is insoluble in water ; it is readily decomposed by heat, losing 
half of its oxygen and being converted into monoxide. It is 
an energetic oxidizing agent. When it is briskly triturated 
with a small quantity of sulphur, the latter is inflamed. 

If lead dioxide be introduced into a test-tube filled with sul- 
phurous acid gas, the latter is immediately absorbed with for- 
mation of lead sulphate. 

SO^ + PbO^ = PbSO* 

Hydrochloric acid poured upon lead dioxide determines the 
formation of lead chloride and the disenarasement of chlorine. 



'to^^^iD^ 



PbO^ -f- 4HC1 = PbCP + CP + 2H^0 

Lead dioxide unites with the alkalies f(5rming veritable salts. 
Fremy has described a plumbate of potassium, K^PbO^ -|- 
3H^0, which crystallizes in cubes, and which is formed when 
dioxide of lead is gently heated with a very concentrated solu- 
tion of potassium hydroxide in a silver crucible. 

PLUMBOSO-PLUMBIC OXIDE (BED LEAD) 

This oxide is prepared by heating massicot in furnaces to a 
temperature that should not exceed 300°. Under these con- 
ditions, the monoxide absorbs oxygen from the air, and is con- 



LEAD SULPHIDE. 349 

verted into a beautiful red powder known as minium or red lead. 
The product obtained by beating lead carbonate or white lead 
in contact with the air is called orange minium. 

Minium is a combination of monoxide and dioxide of lead ; 
its composition is variable, according to the length of time it 
is roasted. It ordinarily corresponds to the formula 

Pb^O* = 2PbO.PbO^ (Jacquelain) 

Sometimes it contains less oxygen, having the composition 

Pb^O^ = SPbO.PbO^ (Mulder) 

Red crystals of the latter composition have been found in 
the fissures of a minium furnace. 

Minium has a scarlet-red color, which becomes much darker 
on heating. It gives up oxygen at a red heat, being reduced 
to monoxide. If red lead be sprinkled with nitric acid, the 
color disappears, giving place to a brown. The nitric acid 
removes the monoxide, forming nitrate, and leaves the brown 
dioxide. 

Minium is used to color sealing-wax and wall-papers. It is 
employed in the manufacture of flint glass, which owes its fasi- 
bility, its perfect transparency and its refractive power, to sili- 
cate of lead. When mixed with stannic oxide, minium serves 
as an enamel for crockery-ware. 

A mixture of red lead and white lead with a small quantity 
of oil is employed as a luting for steam-pipes, and as a cement. 

LEAD SULPHIDE. 

PbS 

G-alena or sulphide of lead occurs in nature in beautiful 
cubical crystals of a bluish-gray color and a metallic lustre ; its 
density is 7.58. It melts at a red heat. When heated in con- 
tact with air, it is converted into oxide and sulphate, and by the 
reaction of an excess of sulphide upon these compounds me- 
tallic lead is produced. Hot faming nitric acid converts lead 
sulphide into sulphate. Concentrated and boiling hydrochloric 
acid transforms it into chloride with evolution of hydrogen 
sulphide. 

&alena is used for glazing common pottery. A broth of 
powdered galena and cow's dung mixed with water is applied 
to the surface of the previously well-dried vessels. 

30 



350 ELEMENTS OF MODERN CHEMISTRY. 

These are now baked, so that the sulphide melts and 
spreads over the surface, the organic matter preventing its 
oxidation. On exposing the articles to a higher temperature 
they become glazed by the formation of a fusible silicate of 
lead. The danger in using ware so glazed for culinary pur- 
poses is. due to the fact that vinegar and other acids dissolve 
the poisonous lead compound. 

LEAD CHLORIDE. 

PbCP 

This body may be obtained as a white, crystalline powder by 
heating litharge with hydrochloric acid. It is deposited as a 
dense, white precipitate when hydrochloric acid is added to a 
concentrated solution of acetate or nitrate of lead. It is not 
very soluble in water; 135 parts of water at 12.5°, or 33 parts 
of boiling water being required to dissolve one part of lead 
chloride. It may be obtained crystallized in long needles by 
allowing its saturated boiling solution to cool. Lead chloride 
melts below a red heat, and on cooling solidifies to a semi-trans- 
parent mass, which was formerly called horn-lead. 

Mineral yelloio^ Turner's yellow ^^ndi CasseZ^eZ/ozo, employed 
in painting, are oxychlorides of lead, combinations of lead 
oxide and chloride in variable proportions. 

Lead Tetrachloride, PbCl*. — When lead dioxide is dissolved 
in hydrochloric acid at very low temperatures, this compound is 
produced. On addition of ammonium chloride it is precipitated as 
the double salt PbCl*.2NH*Cl, and this, treated with strong sul- 
phuric acid at 0°, yields the pure tetrachloride (Friedrich). 

It is a heavy yellow oil, which solidifies at — 15°. "Water decom- 
poses it into lead chloride and chlorine. 

LEAD IODIDE. 

PbI2 

When a solution of potassium iodide is added to a solutior 
of lead acetate, a beautiful yellow precipitate of lead iodide is 
formed. 

This body melts to a red-brown liquid at a high temperature. 
It requires for solution 1235 parts of cold, or 194 parts of 
boiling water. On the cooling of its saturated, boiling solution, 
it is deposited in golden-yellow, hexagonal scales having a mag- 
nificent lustre. 



LEAD NITRATE — LEAD SULPHATE. 351 

LEAD NITRATE. 

Pb(N03)2 

This body is prepared by dissolving litharge in dilute nitric 
acid. It crystallizes from its hot, saturated solution in anhy- 
drous, white, regular octahedra. These crystals decrepitate 
when they are heated; they dissolve in 7 J times their weight 
of cold water, and in a much less quantity of boiling water. 

At a red heat this salt is decomposed into nitrogen peroxide, 
oxygen, and lead monoxide. It forms various basic compounds 
with lead monoxide. 

When one molecule of the nitrate is boiled with one molecule 
of the monoxide, and the filtered solution is allowed to cool, 
a crystalline deposit is obtained, which is a dibasic nitrate, 
Pb(N03)' + PbO + H^O (Pelouze). This salt can be consid- 
ered as derived from orthonitric acid, H^NO* = HNO^ -j- 
H=^0. Indeed 

Pb(NO^)^ + PbO + H^O -= 2^^ I NO* 

This basic nitrate of lead corresponds to the basic nitrate of 
bismuth (page 379). 

Bi'"NO* ^g| NO* 

Bismuth subnitrate. Lead subnitrate. 

When a solution of nitrate of lead is boiled with thin sheet- 
lead, the latter is dissolved, and the liquid assumes a yellow 
color. Under these conditions soluble basic nitrites of lead are 
formed. On cooling the filtered liquid deposits yellow crystals 
having a variable composition. By a prolonged boiling a tetra- 
basic nitrite, Pb(NO')' + 3PbO + H^O, is obtained. "^ The so- 
lution of the latter, decomposed by carbon dioxide, gives the 
neutral nitrite Pb(NO^)^ -J- H^O, crystallizing in long, yellow 
prisms (Peligot) or in yellow plates (Chevreul). 

LEAD SULPHATE. 

PbSO^ 

This salt is found native, and beautifully crystallized, as 
anglesite. It can be prepared by double decomposition by 
precipitating the solution of any soluble lead salt, such as the 
nitrate or acetate, with sulphuric acid or solution of a sul- 
phate. It is a white powder, insoluble in water. 



352 



ELEMENTS OF MODERN CHEMISTRY. 



At a higli temperature, lead sulphate melts without decom- 
position. Charcoal reduces it, transforming it into sulphide, 
metal, or oxide, according to the proportions employed. 
Quickly heated with an excess of charcoal, it yields sulphide. 
PbS0*+C^ = 2C0^ + PbS 
By diminishing the proportion of charcoal, a residue of 
metal, or even of oxide, may be obtained. 

PbSO^ -I- C = CO^ + SO^ + Pb 
2PbS0* 4- C = CO^ + 2S0^ 4- 2PbO 
Iron and zinc, in contact with lead sulphate suspended in 
water, cause the separation of metallic lead. 



LEAD CARBONATE. 

PbCOs 

Crystallized lead carbonate is found in nature as the min- 
eral cerusite. The salt may be obtained artificially, as an 
amorphous white powder, by precipitating a soluble lead salt 
by an excess of an alkaline carbonate. 

A hydrated, and sometimes basic, carbonate of lead is 
known as ceruse or white lead. Its composition varies. 

PbCO^ + WO and 2PbC0' + Pb(OH)'» 

White lead is extensively used as a paint and paint body. 
It is prepared by several methods, the oldest of which is called 
the Dutch process. It consists in exposing sheets of lead to an 
atmosphere charged with acetic acid 
rxs..^v^^ .vs...ss.>.sss..sv..s..s.. .;^s^ vapor and rich in carbonic acid gas. 
The leaden sheets are introduced 
into glazed earthen pots, A (Fig. 
110), containing a small quantity of 
vinegar. The lead rests upon short 
projecting arms, B, below which is 
placed the crude vinegar. The 
pots are covered by a disk of lead, 
D, which incompletely closes them. 
They are then arranged in rows in 
large chambers ; a row of pots is 
placed on a bed of spent tan or horse-manure ; these are cov- 
ered with planks, upon which more spent tan or horse-mantire 
is placed, and then another layer of pots, and so on. The fer- 




FiG. 110. 



LEAD CHROMATE. 353 

mentation of the tan or manure raises the temperature to 30 
or 40°, and produces carbonic acid gas. On the other hand, 
the oxygen of the air intervenes, causing the lead to be 
attacked by the acetic acid, so that basic acetate of lead is 
formed upon the surface of the metal ; but this salt is con- 
tinually decomposed by the carbonic acid gas, so that the lead 
gradually becomes covered with a layer of carbonate. 

Thenard suggested another process by which litharge is dis- 
solved in a solution of lead acetate, and a current of carbon 
dioxide passed through the solution of subacetate so formed. 
Lead carbonate is precipitated and neutral acetate regenerated ; 
the latter is then again transformed into basic acetate. The 
product so obtained is known as Clichy white lead. 

LEAD CHROMATE. 

PbCrO* 

This salt exists crystallized in nature, constituting the 
crocoite of Siberia. It is prepared by double decomposition 
between solutions of potassium chromate and lead acetate ; a 
yellow precipitate is thus obtained, and is employed in painting 
under the name chrome yellow. 

Lead chromate melts at a red heat ; at a white heat it loses 
4 per cent, of oxygen. It is easily reduced by charcoal and 
hydrogen. Insoluble in water, it dissolves readily in solutions 
of potassium hydroxide. 

Characters of Lead Salts. — The soluble lead salts have a 
sweetish taste. Black precipitates are formed in their solutions 
by both hydrogen sulphide and ammonium sulphide. 

The caustic alkalies give white precipitates, soluble in a 
large excess of the reagent. Ammonia gives a white pre- 
cipitate, insoluble in excess. 

Sulphuric acid forms a white precipitate even in the most 
dilute solutions of lead. Hydrochloric acid forms a white 
precipitate of lead chloride, but this precipitate is not produced 
in dilute solutions. 

Potassium chromate throws down a yellow precipitate, soluble 
in potassium hydroxide. 

When heated with sodium carbonate upon a piece of charcoal 
in the reducing flame of the blow-pipe, the lead salts yield a 
metallic globule which when cold can readily be flattened out 
by hammering. 

X 3d* 



354 ELEMENTS OF MODERN CHEMISTHY. 

THALLIUM. 

Tl = 202.6 

The spectroscopic green line given by this metal was first 
observed by William Crookes, who regarded it as characteris- 
tic of a new element. The honor of having isolated the latter 
and of establishing its true character belongs to Lamy. 

Thallium is widely distributed in nature, but constitutes 
only a very small proportion of the minerals in which it occurs, 
excepting the very rare crookesite, which contains 16 to 18 
per cent. 

It is a heavy metal, rather whiter than lead ; it is soft and 
sectile. Its density is 11.9, and it melts at 285°. It is sol- 
uble in dilute sulphuric and nitric acids. 

Thallium forms two oxides, to which correspond two series 
of salts. 

Thallous oxide^ TPO, is a black powder ; the corresponding 
hydroxide, TIOH, is soluble and caustic like the alkalies, and 
crystallizes in yellowish prisms. Thallous chloride, TlCl, is 
sparingly soluble in water. The carbonate, TPCO^ is quite 
soluble in water. 

Thallic oxide^ TPO^ is obtained as a dark powder, when 
thallium burns in oxygen or when the hydroxide is heated. 
The compounds derived from this oxide are less stable 
than the thallous compounds : the chloride TICP, sulphate 
TP(SO*)^, and other thallic salts have been prepared. 



COPPER. 

Cu(Cuprum) = 63.12 

Natural State. — Copper is found in the native state, some- 
times crystallized in isometric forms, sometimes in masses. 
It is also found as cuprous oxide, Cu^O, cupric oxide, CuO, and 
cupric carbonate, CuCO^ ; but its most abundant minerals are 
cuprous sulphide, Cu^S {clialcocite), and a, double sulphide 
of copper and iron, Cu'^S.Fe^S^ designated as copper pyrites. 
Under the name gray copper are also worked various minerals 
containing cuprous sulphide combined with the sulphides of 
antimony and arsenic, and in which the copper is sometimes 
replaced by iron, zinc, silver, and mercury. 

Treatment of Copper Ores. — Copper is easily extracted 
from cuprous oxide and cupric carbonate. These ores are 



COPPER. 



355 



melted with charcoal in suitable furnaces, and the metal is at 
once obtained. Copper pyrites, which is often mixed with 
cuprous sulphide, requires a more complicated treatment. The 
iron and sulphur must be eliminated, and for this reason the 
ore is subjected to an incomplete roasting. This operation is 
conducted in a reverberator j furnace (Fig. 111). The flame 




Fig. 111. 

of the fire sweeps the arched vault of the furnace w. The 
opening of the chimney is at C, and the ore is fed in from iron 
troughs placed above the furnace. 

The first roasting drives out part of the sulphur, and the 
sulphides of iron and copper are partially converted into oxides 
and sulphates. An excess of sulphide remains, and the im- 
perfectly-roasted ore is fused in presence of silicious materials. 
The scoriae formed in roasting the matte (see farther on) are 
generally added, and sometimes fluor spar, to render the slag 
more fusible. This operation is conducted either in cupola-fur- 
naces or in reverberatory furnaces of peculiar construction. In 
presence of the unattacked sulphide of iron, the cupric oxide 
formed during the roasting is converted into cuprous sulphide, 
and oxide of iron is formed. The latter unites with the silica, as 
does also the oxide produced by the roasting, both being reduced 
to ferrous oxide by the redticing gases of the fire. Ferrous sili- 
cate is thus formed, and constitutes a very fusible slag, below 
which accumulates the sulphide of copper containing much less 
sulphide of iron than the original pyrites. This product is the 
matte. 



356 ELEMENTS OP MODERN CHEMISTRY. 

The sulphur, which was thus far necessary to expel the iron, 
must now be removed, and the matte is broken up and repeat- 
edly roasted, by which the remainder of the iron is oxidized 
and nearly all of the sulphur expelled. The mineral is now 
again melted with silicious materials and the scoriae produced 
in refining black copper, and rich in cupric oxide, are added. 
Ferrous silicate separates as a slag, and a metallic mass contain- 
ing from 90 to 94 per cent, of copper, still alloyed with iron, 
lead, arsenic, sulphur, etc., is obtained. This is black copper. 

Instead of reducing matte by successive roasting and melt- 
ing as above, the sulphur is often removed by blowing air 
through the melted material in a vessel resembling a Bessemer 
converter (page 395) and lined with quartz : iron and copper 
are rapidly oxidized, while sulphur dioxide is given ofi". The 
resulting metal is much purer than that obtained by the older 
process. 

Refining of Black Copper. — The impure metal is melted in 
a reverberatory furnace ; the air-holes are then opened, and 
the impurities are partly volatilized, partly oxidized. The 
sulphur is driven off as sulphur dioxide, and iron and other 
metallic impurities, as well as copper, become oxidized and 
pass into the slag. This is skimmed off so that the metal 
may absorb more oxygen, which it transmits to the remaining 
sulphur. Finally the oxygen is eliminated by covering the 
surface of the metal with coal and plunging poles of green 
wood into it. The hydrocarbons and carbon monoxide so 
produced reduce the cuprous oxide to the metal. 

Large quantities of copper are now refined by electrolysis. 
The crude metal is cast in plates which serve as anodes in an 
acid bath of copper sulphate solution, the cathodes being thin 
copper plates. Under the influence of the current the anodes 
are dissolved, and an equivalent quantity of pure copper is 
deposited on the cathodes. The precious metals remain un- 
dissolved, and accumulate in the anode mud at the bottom of 
the tanks, while other impurities, such as arsenic and anti- 
mony, are held in solution. The electrolytic process yields a 
product which is practically free from impurities, and it effects 
the extraction of the gold and silver from crude copper. 

In the Lake Superior region, the native copper is separated 
mechanically from the rock and then subjected to refining 
operations analogous to those first described. The product is 
known as Lake Copper ^ and is of the highest grade. 



COPPER. 357 

Cement copper is copper precipitated from a solution of 
cupric sulphate by metallic iron. It is very pure. 

Properties of Copper. — This metal has a characteristic red 
color that is universally known. When rubbed with the hand 
it exhales a peculiar, disagreeable odor. By fusion it crystal- 
lizes in cubes, but it may be deposited by electrolysis in reg- 
ular octahedra. It melts towards 1100°, and maybe volatilized 
by the heat of the oxyhydrogen blow-pipe or in the electric 
furnace. 

Its density varies from 8.85 to 8.95. It is very malleable, 
ductile, and tenacious. 

In dry air it is unaltered at ordinary temperatures, but it 
absorbs oxygen in presence of moisture and carbonic acid gas. 
Grreen spots are then formed upon the surface of the metal, 
constituting a hydrocarbonate of copper; this is the product 
ordinarily called verdigris. 

At a high temperature copper absorbs oxygen with avidity, 
being converted into black, cupric oxide if the oxygen be in 
excess ; but in the contrary case, red, cuprous oxide is formed. 
The oxidation is favored by division of the metal. 

If some pulverulent copper, produced by the decomposition 
of copper acetate, be thrown upon a moderately hot tile and an 
incandescent coal be approached so as to heat one point, a black 
spot instantly forms there and rapidly extends throughout the 
mass, showing the progress of the oxidation. 

In presence of acids or ammonia, copper rapidly absorbs 
oxygen at ordinary temperatures. 

If some ammonia and copper-turnings be shaken up with air 
in a glass-stoppered bottle, the ammoniacal liquid becomes blue; 
if now the bottle be turned upside-down and opened under 
water, the latter will rise in the bottle, replacing the. oxygen 
which was absorbed. The blue liquid contains in solution am- 
moniacal oxide of copper and nitrite of copper (Schonbein, 
Peligot). 

This liquid is capable of dissolving cotton and lint, which 
are almost pure cellulose (Schweizer). 

"When heated with concentrated sulphuric acid, copper is 
converted into sulphate with disengagement of sulphurous 
acid gas. Nitric acid, even dilute, dissolves it readily, forming 
cupric nitrate and evolving nitric oxide. Boiling hydrochloric 
acid attacks it slowly, disengaging hydrogen and forming 
cuprous chloride. 

Uses of Copper. — Copper is much employed for the con- 



358 ELEMENTS OP MODERN CHEMISTRY. 

struction of boilers, alembics, stills and worms, and for kitchen 
utensils. Owing to its high electric conductivity, enormous 
quantities are used in electric constructions for cables, dyna- 
mos, etc. Sheet-copper is used for coating the bottoms of ships 
and sometimes for roofing houses. This metal enters into the 
composition of many important alloys, such as brass, varioufe 
bronzes, and Grerman silver. 

CUPROUS OXIDE. 

Cu^O 

This oxide is found native as cuprite^ sometimes in vitreous 
masses, sometimes in beautiful, red, regular octahedra. 

It is ordinarily prepared in the wet way by boiling a solution 
of acetate of copper with glucose ; a bright-red, crystalline pow- 
der is precipitated, which is anhydrous cuprous oxide. When 
heated in contact with air, it absorbs oxygen and is converted 
into cupric oxide. 

When caustic potash is added to a solution of cuprous 
chloride, a yellow precipitate of cuprous hydroxide is thrown 
down. Cuprous oxide is used to communicate a red color to glass. 

CUPRIC OXIDE. 

CuO 

Two processes are used for the preparation of this important 
body : calcination of copper in the air ; calcination of cupric 
nitrate. The first method furnishes a granular, compact, black 
oxide ; the second, a fine, deep-black powder. 

Cupric oxide is easily reduced by both hydrogen and char- 
coal, with formation of either water or carbon dioxide. 

Cupric hydroxide^ Cu(OH)^, is obtained as a voluminous, 
light-blue precipitate when caustic potash is added to the solu- 
tion of a cupric salt. This hydroxide is converted into brown, 
anhydrous oxide by boiling with water. Cupric oxide is 
largely used in the laboratory in the analysis of organic sub- 
stances. It is used in the arts to color glass, to which it im- 
parts a green color. 

SULPHIDES OF COPPER. 

Copper forms two sulphides, corresponding to the oxides. 
Cuprous sulphide, Cu^S, occurs in nature as chalcocite in 
fusible, steel-gray crystals, which may be scratched with a 
knife. 



CHLORIDES or COPPER— OUPRIC SULPHATE. 359 

Cupric sulphide CuS, is formed in tlie wet way when a 
solution of a copper salt is precipitated by hydrogen sulphide. 
When strongly calcined, it loses sulphur and is reduced to 
cuprous sulphide. 

If copper filings or turnings be thrown into a flask containing 
boiling sulphur, a brilliant incandescence takes place from the 
union of the two elements. 

CHLORIDES OF COPPER. 

Cuprous chloride, CuCl, is prepared by boiling copper- 
turnings in hydrochloric acid and adding small quantities of 
nitric acid from time to time. The nitro-muriatic acid formed 
converts the copper into cupric chloride, which is reduced by 
the excess of copper present. A brown liquid is thus obtained 
which, by continued boiling, becomes almost colorless. On 
adding water to this liquid, a white, crystalline precipitate of 
cuprous chloride is deposited. It is insoluble in water, but dis- 
solves in aqueous ammonia, forming a liquid which remains 
colorless when kept in closed vessels in presence of an excess 
of copper, but becomes blue on exposure to the air, from which 
it absorbs oxygen. 

Carbon monoxide is perfectly absorbed by a solution of 
cuprous chloride in hydrochloric acid or in ammonia. 

Cupric chloride, CuCP, is obtained by dissolving cupric oxide 
in hydrochloric acid or copper in aqua regia. A green solu- 
tion is formed, which, after concentration, deposits beautiful 
rhombic prisms of a bluish-green color, containing 2 mole- 
cules of water of crystallization. 

CUPRIC SULPHATE. 

CuSO* + 5H20 

Preparation. — This salt is commonly called blue vitriol. It 
is a product of many industrial operations, such as roasting 
sulphurous copper ores, and the decomposition by copper of 
the silver sulphate resulting from the refining of gold, — that 
is, the treatment of silver coin containing gold with sulphuric 
acid. 

Cupric sulphate produced by roasting copper ore contains 
more or less ferrous sulphate. The two salts crystallize together 
in monoclinic prisms, containing 7 molecules of water of 
crystallization. The mixture is called Salzburg vitriol. 



360 ELEMENTS OF MODERN CHEMISTRY. 

Instead of copper pyrites, artificial cupric sulphide may be 
oxidized. Old copper plates are moistened and sprinkled with 
flowers of sulphur; they are then heated in a furnace, and the 
sulphide of copper first formed is converted into sulphate by 
the oxygen of the air drawn into the furnace. The still hot 
plates are plunged into water, which dissolves the layer of cupric 
sulphate, and the same operation is repeated until all of the 
metal is transformed into sulphate. 

The simplest process consists in boiling copper turnings and 
clippings with sulphuric acid : sulphurous acid gas is disen- 
gaged, and cupric sulphate formed. In the arts, the operation 
is conducted in wooden tanks lined with lead and heated by 
steam. 

Properties. — Cupric sulphate crystallizes in large tabular 
forms belonging to the triclinic system. These crystals have 
a fine blue color, and contain 5 molecules of water. When 
exposed to dry air they effloresce superficially : heated to 100°, 
they lose 4 molecules of water, disengaging the fifth only at 
243°. The anhydrous salt is white. At a high heat, cupric 
sulphate is decomposed into cupric oxide, sulphurous oxide, 
and oxygen. 

Cupric sulphate dissolves in 4 parts of cold, and in 2 parts 
of boiling water, and the concentrated solution has a pure blue 
color. It is insoluble in alcohol. 

When an excess of ammonia is added to a solution of cupric 
sulphate, a beautiful, dark-blue liquid is obtained. It contains 
ammoniacal cupric sulphate, CuSO* -|- 4NH^ -\- H^O, which 
separates in dark-blue crystals when alcohol is added to the 
aqueous solution. 

There are several basic sulphates of copper representing 
compounds of cupric sulphate and cupric hydroxide. One of 
tbem is obtained as a green powder when a solution of cupric 
sulphate is digested with cupric hydroxide. The bluish pre- 
cipitates obtained by incompletely precipitating solutions of 
cupric sulphate with potassium hydroxide are basic sulphates. 

Uses. — Cupric sulphate is employed as a caustic applicable 
to diseases of the eye. In the arts, it is used in the prepara- 
tion of blue ashes, a mixture of calcium sulphate and cupric 
hydrate, made by decomposing cupric sulphate with milk of 
lime. 

It is much used in dyeing, particularly in dyeing black on 
wool and cotton. It is also employed for preserving wood. 



CARBONATES OF COPPER — ALLOYS OF COPPER. 361 

Large quantities of sulphate of copper are employed for elec- 
trotyping, and for electric batteries. 

CARBONATES OF COPPER. 

When cold solutions of sodium carbonate and cupric sul- 
phate are mixed, a bluish-green precipitate is obtained, and at 
the same time carbonic acid gas is disengaged. The precipi- 
tate becomes gTeen when washed with warm water. It is 
known as mineral green, and can be regarded as a combina- 
tion of one molecule of cupric carbonate with one molecule of 
cupric hydroxide. It contains 

CuCO^ + Cu(0H)2 

A similar compound exists in nature, constituting malachite. 
This mineral occurs in green masses. When cut and polished, 
it presents veins of various tints, and is fashioned into orna- 
mental objects, such as vases, cups, etc. 

AzuTite or mountain blue, which crystallizes in beautiful, 
blue, oblique rhombic prisms, can be regarded as a compound 
of two molecules of cupric carbonate with one of the hydrate. 

2CuC0^ + Cu(OH)^ 

Debray has reproduced azurite artificially by leaving calcium 
carbonate for a long time in contact with cupric nitrate in 
sealed tubes. 

ALLOYS OF COPPER. 

Brass is an alloy of copper and zinc, ordinarily containing ^ 
zinc and f copper. It often contains a small proportion of tin 
and even of lead. 

Bronze is an alloy of copper and tin (see table of alloys, page 
249). While brass is malleable and ductile, bronze is brittle 
when it has been slowly cooled, but it becomes malleable after 
tempering, — that is, when it is heated to redness and then 
plunged into cold water. 

Grerman silver contains 25 per cent, of zinc, 25 of nickel, 
and 50 of copper. 

Aluminium-bronze, phosphor-bronze, manganese-bronze, 
and silicon-bronze are very tenacious and valuable alloys of 
copper with the elements indicated by the names. Silicon- 
bronze is used for telegraph-wires, and manganese-bronze for 
Q 31 



S62 ELEMENTS OF MODERN CHEMISTRY. 

the propellers of ships, as it resists the corroding action of 
salt water and is remarkably tenacious. 

Characters of Copper Salts. — These salts are blue or green. 
Their solutions are precipitated brown by hydrogen sulphide 
and ammonium sulphide ; an excess of the latter reagent will 
not dissolve the precipitate. 

Potassium hydroxide forms a dense, light-blue precipitate, 
insoluble in excess. Ammonia-water first forms a pale-blue 
precipitate, which is then dissolved by an excess of the reagent 
with a rich sky-blue color. 

Potassium ferrocyanide gives a reddish-brown precipitate 
even in very dilute cupric solutions. 

An apple-green precipitate of cupric arsenite (Scheele's 
green) is formed when potassium arsenite is added to cupric 
sulphate. 

A bright piece of iron plunged into a cupric solution in- 
stantly becomes covered with a deposit of metallic copper. 



MERCURY. 

Hg (Hydrargyrum) = 200 

Natural State and Extraction. — Mercury occurs native, 
and especially combined with sulphur, mercuric sulphide or 
natural cinnabar being its principal ore. It is found in differ- 
ent localities in Europe and America, principally at Almad'en, 
Spain ; Idria, in Carniola ; and in California. 

The treatment of the ore is very simple. The sulphide is 
roasted in a current of air in furnaces of peculiar construction : 
the sulphur is oxidized, and passes off as sulphur dioxide, the 
mercury being set free. The metal volatilizes and is led, to- 
gether with the gases from the combustion, either into con- 
densation-chambers, or through long rows of little cylindrical 
vessels, where the mercury condenses. 

Fig. 113 represents the furnaces employed at Almaden, 
with the fireplace, and the body, AB, charged with ore. The 
mercury-vapor passes by o, and condenses in a series of aludels 
entering one in the other, and arranged upon two inclined planes, 
ah^ he. The condensed metal runs into a channel, 6, from 
which it is conducted into a reservoir. The sulphurous acid 
gas, still charged with vapor of mercury, passes into a chamber, 
C, descending to the floor, where it is cooled by conta.ct with a 



MERCURY. 



363 



trougli filled with water, d. In this chamber the condensa- 
tion of the mercury- vapor is completed. 




Fig. 113. 

Fig. 114 represents the several-storied furnaces aa, hh, cc, 
and the condensation-chambers CC, used at Idria. 

Cinnabar may also be reduced by iron or by lime. 

The metal thus extracted is purified by filtration through 
ticking-cloth or chamois-skin. It is ordinarily transported in 
forged iron bottles. 




Fig. 114. 



The mercury of commerce is nearly always alloyed with 
small quantities of other metals, such as lead, tin, copper, and 



364 ELEMENTS OF MODERN CHEMISTRY. 

bismuth. In this state its surface is not as brilliant as when 
pure, it does not run as readily, and the drops are drawn out 
to a point. They are said to form tails. It may be purified by 
distillation, an operation which requires certain precautions 
on account of the violent bumping of boiling mercury. This 
distillation is best effected under diminished pressure. Mer- 
cury may also be purified by digesting it for several days with 
one-thirtieth its weight of commercial nitric acid diluted with 
its own weight of water ; the aqueous liquid is then decanted 
and the mercury washed, first with warm water acidulated with 
nitric acid, then with pure water, after which it can be dried. 
In this operation, the nitric acid removes the foreign metals, 
more oxidizable than the mercury, which displace the latter 
metal from its solution in the nitric acid. 

Properties. — Mercury is liquid, but solidifies at — 40°. The 
solid metal at this low temperature is malleable, and has a 
density of 14.4. The density of liquid mercury is 13.595. It 
boils at 350° of an air thermometer. Its vapor is colorless, 
and has a density of 6.976. 

It is unaltered by contact with the air at ordinary tempera- 
tures, but at 300° it slowly absorbs oxygen, and its surface 
becomes covered with a red powder, which is mercuric oxide, 
called by the ancients red precipitate. 

Mercury combines with chlorine, bromine, and iodine at ordi- 
nary temperatures, and with sulphur by the aid of a gentle heat. 

Hydrochloric acid does not attack it. Dilute nitric acid dis- 
solves it in the cold, forming mercurous nitrate. Hot nitric 
acid dissolves it, forming mercuric nitrate and evolving red 
vapors. 

OXIDES OF MERCURY. 

Two oxides of mercury are known, mercurous oxide, Hg^O, 
and mercuric oxide, HgO. 

The first is prepared by digesting mercurous chloride with 
potassium hydroxide; a black powder is obtained which is 
very unstable. By the action of light, or by a temperature above 
100°, it decomposes into mercuric oxide and mercury. 

Mercuric Oxide, HgO, can be obtained by either the dry or 
wet method. The first consists in decomposing mercuric nitrate 
by heat; the salt is gradually heated in a flask on a sand- 
bath until red vapors cease to be disengaged. 



MERCtmiC SULPHIDE. 365 

The oxide thus prepared is an orange-red, granular, and 
crystalline powder. 

Mercuric oxide is prepared in the wet way by decomposing 
a solution of mercuric chloride by caustic potash. A yellow 
precipitate of anhydrous mercuric oxide is obtained. 

When mercuric oxide is heated, it assumes a dark-red color 
and decomposes, if the temperature be above 400°, into oxygen 
and mercury. It yields its oxygen to many bodies, such as 
charcoal, sulphur, and phosphorus, which it oxidizes energet- 
ically. When heated with sulphur, it produces an explosion. 
In these reactions the finely-divided yellow oxide is more active 
than the red oxide. 

MEECURIC SULPHIDE. 

HgS 

This is the cinnabar generally found in nature in compact 
masses, sometimes in transparent, red, hexagonal prisms or 
rhombohedra. It is manufactured by directly combining sul- 
phur and mercury. The combination takes place when the 
bodies are triturated together in the cold, in the proportion of 
100 parts of mercury and 18 parts of sulphur. A black mass 
is thus obtained which is sublimed in iron vessels. 

Cinnabar prepared by sublimation occurs in dark-red masses, 
having a fibrous and crystalline structure. Its density is 8.124. 
At a high temperature, it volatilizes without melting. When 
heated in the air, it burns with a blue flame, yielding sulphur- 
ous acid gas and metallic mercury. It is decomposed by hydro- 
gen, charcoal, and most of the metals. Boiling sulphuric acid 
decomposes it with formation of sulphurous acid gas and sul- 
phate of mercury. Nitric acid scarcely attacks it, even when 
boiling. 

Vermilion is a finely-divided mercuric sulphide having a 
rich scarlet color. It is prepared by triturating for several 
hours in a mortar, 300 parts of mercury and 114 parts of 
flowers of sulphur, and adding to the black sulphide thus ob- 
tained 75 parts of caustic potash and 400 parts of water. The 
mixture is maintained at a temperature of about 45°, being 
continually triturated with a pestle. As soon as the powder 
has acquired a fine scarlet color, it is rapidly washed with hot 
water and dried. It is employed in painting and also to color 
sealing-wax. 

31* 



366 ELEMENTS OP MODERN CHEMISTRY. 



MERCUROUS CHLORIDE, OR CALOMEL. 
HgCl 

Mercurous chloride is largely used in medicine under the 
name calomel or mild chloride of mercury. 

Preparation. — An intimate mixture of mercurous sulphate 
and sodium chloride is heated in a capacious glass matrass on 
a sand-bath. The mercurous chloride, formed by double decom- 
position, sublimes. 

Hg^SO^ + 2NaCl == 2HgCl + Na^SO* 

It is thus obtained in compact, crystalline masses. When 
it is strongly heated and its vapor passed into large stoneware 
vessels filled with steam, it condenses in an impalpable powder, 
in which form it is used by preference in medicine. 

Calomel may also be prepared in the wet way by adding 
hydrochloric acid, or a solution of sodium chloride, to a solu- 
tion of mercurous nitrate. A white, curdy precipitate is 
obtained which is washed and dried. 

Properties. — Prepared in the dry way calomel occurs as 
dense, fibrous, crystalline and slightly transparent masses, one 
side of which is smooth, the other presenting the sharp points 
of the crystals. When exposed to light, it becomes yellow and 
even gray in time, being partially decomposed. Its density is 
7.17. It melts and volatilizes at the same temperature : the 
density of the vapor is 8.12, and corresponds to the formula 
HgCl, which is analogous to that of silver chloride. When 
slowly sublimed, calomel crystallizes in tetragonal prisms. It 
is insoluble in water. 

A solution of potassium iodide agitated with calomel con- 
verts it into a green powder of mercurous iodide. If an excess 
of potassium iodide be employed, the green powder disappears 
and is replaced by a gray precipitate of metallic mercury, the 
mercurous iodide at first formed being decomposed into mercury 
and mercuric iodide, which dissolves in the potassium iodide. 

An analogous reaction takes place with the alkaline chlorides 
by the aid of heat, the mercurous chloride breaking up into 
mercuric chloride which dissolves, and metallic mercury which 
is deposited. 



MERCURIC CHLORIDE, OR CORROSIVE SIJBLIMATE. 367 

MERCURIC CHLORIDE, OR CORROSIVE SUBLI- 
MATE. 

HgCP 

Preparation. — This body is obtained by double decomposi- 
tion, by heating a mixture of mercuric sulphate and sodium 
chloride on a sand-bath. The mercuric chloride condenses in 
the upper part of the matrasses which are imbedded up to the 
neck in the sand. 

HgSO^ + 2NaCl = Na^SO^ + HgCP 

Towards the close of the operation the heat is increased in 
order to agglomerate the sublimate by a partial fusion. 

Another process consists in passing chlorine into heated 
mercury ; the combination takes place with the production of 
luminous heat. 

Properties. — IMercuric chloride prepared by the dry method 
occurs in compact, white, crystalline and friable masses, having 
a density of 6.5. It is an energetic poison. It melts at about 
265°, and boils towards 295°. The density of its vapor is 
9.42. By sublimation it may be obtained crystallized in rec- 
tangular octahedra. 

It is soluble in 19 parts of cold water, also in alcohol and ether. 
It is deposited from its hot, saturated, aqueous solution in 
long prisms, belonging to the type of the right rhombic prism. 
The crystals are anhydrous. 

The aqueous solution of mercuric chloride produces a white 
precipitate in a solution of albumen of white of egg. This 
precipitate is a combination of mercuric chloride and albumen. 
Albumen is thus the antidote to corrosive sublimate. Corro- 
sive sublimate is one of the most powerful antiseptics : it is 
used in surgery, medicine, taxidermy, preserving wood, etc. 

When a slight excess of ammonia is added to a solution 
of corrosive sublimate, a white deposit is formed, known as 
ichite precipitate, of which the composition is HgH^NCl. 
HgCP + 2XH^ = XH^Cl -L HgH^NCl 

It may be regarded as the chloride of mercury-ammonium, 
that is, ammonium chloride in which 2 atoms of hydrogen are 
replaced by one atom of the diatomic metal mercury. 

Ho^' 
HgH^NCl = H ^ NCI 
H 



368 ELEMENTS OE MODERN CHEMISTRY. 

Corrosive sublimate forms crystallizable double combina- 
tions with the alkaline chlorides and with ammonium chloride. 

MERCUROUS IODIDE. 
Hgl 

This compound is ordinarily prepared by directly combining 
mercury and iodine. 100 parts of mercury and 63.5 parts of 
iodine are triturated with a small quantity of alcohol, until the 
whole is converted into a green powder, which is then washed 
with boiling alcohol and dried. 

It may also be prepared by double decomposition by precipi- 
tating a solution of mercurous nitrate with potassium iodide, 
or by the reaction of the latter body upon calomel. 

Mercurous iodide is not a stable compound. It is decom- 
posed by light. Heat breaks it up into mercury and mercuric 
iodide, and the same decomposition is effected by potassium 
iodide and the alkaline chlorides. 

MERCURIC IODIDE. 

HgP 

Mercuric iodide is prepared by pouring a solution of 100 
parts of potassium iodide into a solution of 80 parts of corro> 
sive sublimate. A beautiful scarlet-red precipitate of mercuric 
iodide is thrown down. 

It is necessary that the bodies be employed in the propor- 
tions indicated ; an excess of potassium iodide would dissolve 
the mercuric iodide first precipitated. 

Mercuric iodide is almost insoluble in water ; it is slightly 
soluble in boiling alcohol, which deposits it on cooling in small 
red octahedral crystals. 

If mercuric iodide be heated in a small glass retort, it melts 
to a dark-yellow liquid which solidifies on cooling to a yellow 
mass. At a higher temperature the liquid boils and its vapor 
condenses in a dark-yellow liquid which solidifies to a yellow 
mass ; at the same time, right rhombic prisms of a yellow color 
sublime. If these be rubbed with a glass rod or other hard 
body they instantly become red, first at the point of contact, 
then throughout the entire mass. 

These two forms of mercuric iodide constitute one of the 
most curious examples of dimorphism. 

Mercuric iodide forms a combination with potassium iodide 



NITRATES OF MERCURY SULPHATES OF MERCURY. 369 

which is soluble in water. A solution of this potassium-mer- 
curic iodide is not precipitated by potassium hydroxide, but the 
liquid rendered alkaline by the latter reagent is a very sensi- 
tive test for ammonia (JSfesslers test), with which it gives a pre- 
cipitate or a brown cloud more or less intense, according to the 
quantity of ammonia present. 

NITRATES OF MERCURY. 

Neutral mercurous nitrate, HgNO'^ -f H'^0, is obtained 
by the action of an excess of cold, dilute nitric acid upon 
metallic mercury. After some time, short colorless prisms are 
formed in the liquid, constituting the neutral salt. The latter 
is readily soluble in water charged with nitric acid. 

When mercury is attacked by an excess of boiling nitric 
acid and the solution is evaporated, voluminous crystals of a 
basic mercuric nitrate separate, Hg(NO^)^.HgO -f- 2H^0. 

The syrupy liquid from which these crystals are deposited, 
contains neutral mercuric nitrate. 

Hg(N0=')^+4PP0 

This salt is deposited in large, colorless, rhombic tables when 
the syrupy solution is cooled to — 15°. 

A large quantity of cold water decomposes this nitrate into 
nitric acid which dissolves, and a basic salt, Hg(NO^)^2HgO 
-f- H^O, forming a yellow powder. 

SULPHATES OF MERCURY. 

There is a mercurous sulphate, Hg^SO*, and a mercuric 
sulphate, Hg"SO*. 

The first is obtained by heating equal parts of mercury and 
sulphuric acid, arresting the operation when two-thirds of the 
mercury are converted into a white, crystalline powder. Mer- 
curous sulphate is but slightly soluble in cold water. 

To prepare mercuric sulphate, 1 part of mercury and IJ 
parts of sulphuric acid are heated to dryness on a sand-bath. 
Hg + 2ff SO* ^ 2W0 + HgSO* + SO^ 

It is well to add a small quantity of nitric acid before drying. 

Mercuric sulphate is an anhydrous, white powder. It decom- 
poses at a red heat into metallic mercury, sulphurous acid gas, 
and oxygen. Charcoal reduces it readily, equal volumes of 
carbon dioxide and sulphur dioxide being disengaged. 

y 



3'rO ELEMENTS OP MODERN CHEMtSTRt^. 

Mercuric sulphate is slightly soluble in water : a large quan- 
tity of cold water converts it into a yellow, basic salt, HgSO*. 
2HgO, known as tiirpeth mineral. 

Characters of Mercuroiis Salts. — Their solutions are pre- 
cipitated black by hydrogen sulphide, and also by potassium 
hydroxide and ammonia. Hydrochloric acid gives a white 
precipitate which is blackened by ammonia. Potassium iodide 
forms a green precipitate of mercurous iodide, converted by 
an excess of the reagent into mercuric iodide which dissolves, 
and gray metallic mercury. 

Characters of Mercuric Salts. — Solutions of mercuric salts 
are precipitated black by an excess of hydrogen sulphide, and 
by ammonium sulphide. 

Potassium hydroxide forms a yellow precipitate, insoluble 
in excess. 

Ammonia yields a white precipitate in solutions of corrosive 
sublimate. 

Hydrochloric acid does not precipitate the mercuric salts. 

Iron, zinc, and copper precipitate metallic mercury from 
both mercurous and mercuric solutions. A strip of copper 
dipped into such solutions becomes covered with a gray coating 
which acquires brilliancy by rubbing. 

Heated with lime in a glass tube, all of the mercury com- 
pounds yield metallic mercury which sublimes in small globules, 
easy to recognize under the microscope, and which can be char- 
acterized by the addition of iodine, the vapor of which converts 
the metallic globules into yellow or red mercuric iodide. 

Atomicity of Copper and Mercury.— Copper and mer- 
cury form two series of compounds. In the cuprous and mer- 
curous compounds they resemble silver, playing the part of 
monatomic elements. In other compounds, constituting the 
cupric and mercuric series, these metals are distinctly diatomic, 
like those of the magnesium group. 



VANADIUM. 

V = 51 

Vanadium, niobium, tantalum, thallium, gold, and bismuth 
constitute a class of triatomic or pentatomic elements. The 



NIOBIUM AND TANTALUM. 371 

first three are more closely related to the non-metallic bodies 
than to the metals, and might properly be considered as mem- 
bers of the group of which nitrogen and phosphorus are types. 

Vanadium is widely disseminated, occurring as vanadates 
of lead, copper, bismuth, zinc, calcium, etc., and in many 
argillaceous iron ores, but always in small quantity. 

The compounds of the metal may be prepared most readily 
from the native vanadates vanadhiite or mottramite. The 
powdered mineral is dissolved in hydrochloric acid, the solu- 
tion concentrated, and ammonium chloride added; ammonium 
metavanadate separates. This is repeatedly recrystallized and 
converted into vanadic oxide, V^O^, by gentle ignition. 

By heating vanadic oxide in hydrogen, it is converted into 
the trioxide Y^O^ and with carbon it may be reduced to the 
dioxide Y'^O^ The metal has been obtained by the long- 
continued action of perfectly pure hydrogen upon the dichlo- 
ride YCP at a red heat (Roscoe), and also by heating the 
oxides with charcoal in the electric furnace (Moissan). 

Its chemical relations place vanadium in the nitrogen 
group : the vanadates are isomorphous with the phosphates 
and arsenates. The oxides known are Y^O, Y^O^ Y^O^ 
Y==0*, and Y^0^ and the chlorides YCP, YCP, and YCP have 
been obtained ; there are also oxychlorides. 

Although vanadium is not very abundant, vanadic acid is 
employed in certain dyeing operations, by reason of the facility 
with which it passes to a lower stage of oxidation and again 
becomes oxidized, thus transferring oxygen from the air to 
the dye stuff. Metavanadic acid, HYO*, is a brilliant yellow, 
metal-like substance, and has been proposed as a substitute 
for gold bronze. 



NIOBIUM AND TANTALUM. 

Nb = 94 Ta = 182 

These elements are associated in several minerals, and ^rere 
regarded as identical until 1846. Their principal sources are 
cdumhite, a niobate of iron and manganese, (NbO^)^FeMn, in 
which more or less of the niobium is usually replaced by tan- 
talum ; tantalite^ a ferrous tantalite, Fe(TaO^J^ in which in like 
manner a portion of the tantalum is replaced by niobium ; pyro- 
chlorite^ fergusonite^ yttrotantalite, and euxeriite, in which these 
elements are associated with yttrium, cerium, etc. 



372 ELEMENTS OP MODERN CHEMISTRY. 

Niobium was obtained as steel-gray crusts by Roscoe, who 
passed through a red-hot tube the vapor of niobium chloride 
mixed with hydrogen. Its specific gravity is 7.06 ; it oxidizes 
with incandescence when heated in the air, and burns also in 
chlorine. 

There are three oxides of niobium, Nb'O^ Nb'O*, and Nb'O^ 
A mixture of the latter with the corresponding tantalic oxide 
may be obtained by fusing niobiferous minerals with potassium 
acid sulphate, and boiling the fused mass with water. The res- 
idue is digested with ammonium sulphide, and the remaining 
powder boiled with hydrochloric acid. The two oxides, which 
are unaffected by this treatment, are then separated by convert- 
ing them into fluotantalate and fluoniobate of potassium ; the 
latter is much more soluble than the former. The potassium 
salts are then decomposed by boiling with sulphuric acid. 

Niohic oxide, Nb^O^, is a white, insoluble, infusible powder, 
which is yellow while hot. When strongly heated in hydrogen 
it is reduced to the tetroxide, a bluish-black powder, which 
burns into the pentoxide when heated to redness in the air. 

Niobium pentoxide is the anhydride of niobic acid, HNbO^ 
which is obtained as a white powder by the reaction of niobium 
pentachloride, NbCl^, with water. The normal niobates have 
the general composition R'NbO^, and there is also a series of 
highly complicated niobates, derived from an unknown hydrate, 
H^Nb^O^^ -f nH^O. 

Niobium forms two chlorides, NbCP and NbCP, and an oxy- 
chloride, NbOCP. 

Tantalum has probably not been obtained in a pure state. 
Berzelius obtained it as a black powder by heating potassium 
fluotantalate with potassium. 

There are two oxides, Ta'O* and Ta^O^ Tantalic oxide is 
separated from the niobic acid, with which it is associated in its 
minerals, by the process already indicated. It is a white, infu- 
sible powder, and becomes crystalline when heated. By strong 
ignition with charcoal it is converted into the tetroxide. 

Tantalic acid, HTaO^ is analogous to niobic acid, and forms 
corresponding series of salts. 

Tantalum chloride, TaCP, is formed by heating an intimate 
mixture of tantalic oxide and charcoal in a current of chlorine. 
Niobic chloride is formed in a similar manner. Both are fusi- 
ble, volatile solids, crystallizing in yellow needles. There is no 
tantalum chloride corresponding to the niobous chloride NbCP. 



GOLD. 



373 



GOLD. 

Au (Aurum) = 195.74 

Natural State. — Gold is one of the most anciently known 
metals. It is generally found in the native state, either in 
streaks or veins, or in sand. It ordinarily occurs in scales or 
rounded grains disseminated in alluvial sands, or in the rocks 
whose disintegration produces such sands. It is well known 
that gold-dust is suspended in the waters of certain rivers. 

It is often found associated with ores of silver, lead, and 
copper; sometimes in combination with tellurium. 

Extraction. — Gold is extracted from auriferous sand by 
washings, which remove the particles lighter than the gold. 
The sand, pebbles, and gold, and a strong stream of water 
are thrown into long wooden sluices arranged in zig-zag and 
provided with pockets ; in the latter the gold sinks, while the 
lighter earthy material is carried on by the force of the 
stream. When the gold is in particles too minute to be 
separated mechanically from the sand, which still remains in 
small quantity, the whole is agitated with mercury ; the gold 




Fig. 115. 

dissolves. The amalgam thus obtained is compressed in a 
chamois-skin, which allows the passage of the excess of mer- 
cury. When the solid residue is distilled the gold remains. 

Auriferous quartz rocks are crushed to powder, which is then 
subjected to washings. Mercury is sometimes employed to ex- 
tract the gold from the pulverized rock. The following process 
has been employed for some years in California and Australia. 
The crushed rock, with mercury, water, and two cast-iron balls, 
is introduced into basins, to wnich a rotating motion is given 

32 



374 ELEMENTS OF MODERN CHEMISTRY. 

(Fig. 115). By the friction of the balls it is soon reduced 
to an impalpable powder, wbicb remains suspended in the 
water, and is carried out with the latter through openings in 
the upper part of the basins, while the gold amalgamates 
with the mercury. 

Another process, known as the cyanide process^ depends 
upon the solubility of finely divided gold in solution of potas- 
sium cyanide. A double cyanide of gold and potassium is 
formed, from which the gold is precipitated by metallic zinc. 

4Au + 8KCN + 2H-^0 -f 0^ == 4KAu(CN7 + 4K0H 
2KAu(CN)'^ + Zn = K^ZnCCN)* -f 2Au 

From sulphide ores (pyrites) gold may be extracted by 
means of chlorine. The roasted ore is moistened and treated 
with chlorine gas. The mass is exhausted with water, when 
auric chloride goes into solution and the gold is precipitated 
by means of ferrous sulphate. 

Native gold, as well as that extracted from difi'erent minerals, 
is nearly always alloyed with silver. The two metals are sep- 
arated by the wet way, by attacking the alloy with either nitric 
or sulphuric acid. Nitrate or sulphate of silver is formed, the 
latter being soluble in hot water. The gold remains in a pul- 
verulent state. It is to be remarked that the alloy of gold and 
silver must be rich in silver in order that this process, called 
refining, can be applied. Hence it is sometimes necessary to 
increase the proportion of silver by melting the alloy with that 
metal. 

An alloy of gold and silver rich in gold may also be treated 
with aqua regia. Both metals are converted into chlorides; 
that of silver is insoluble, while that of gold dissolves. When 
ferrous sulphate is added to the yellow solution of chloride of 
gold, a precipitate of metallic gold is obtained, the chlorine 
acting upon the iron of the ferrous sulphate which is thus 
transformed into ferric salt. 

Properties of Gold. — Pure gold has a beautiful yellow color. 
In thin leaves it is translucent, allowing the passage of a green- 
ish light. Its density is 19.5. It is quite soft, and is the most 
malleable and most ductile of the metals. 

It melts at 1075°, and volatilizes at a higher temperature. 
Its vapor is green. 

It is unaltered by the air at all temperatures. Sulphuric, 
hydrochloric, nitric, and phosphoric acids have no action on it 



OXIDES OF GOLD — CHLORIDES OF GOLD. 375 

either in the cold or when aided by heat. It is dissolved by 
nitro-hydrochloric acid. 

Some gold leaf may be boiled with hydrochloric acid in a 
test-tube ; the gold will resist the action of the acid, and will 
retain its lustre. Some more gold leaf may be boiled with pure 
nitric acid in another tube, and again the metal will not be 
attacked. But on mixing the two liquids, the gold will be dis- 
solved with disengagement of red vapors. Grold trichloride will 
be formed, and will color the liquid yellow. 

OXIDES OF GOLD. 

There are two compounds of gold and oxygen, a monoxide, 
Au^O, and a trioxide, Au^Ol The latter forms compounds 
with the bases. When magnesia is added to solution of auric 
chloride, an insoluble yellow precipitate of magnesium aurate 
is formed ; when this is decomposed by nitric acid it leaves auric 
hydroxide. This hydroxide is yellow ; it easily parts with its 
water, and is eonverted into a brown-black powder of auric 
oxide. The latter is not stable, being decomposed by light and 
by a temperature of about 250°. 

CHLORIDES OF GOLD. 

Aurous chloride, AuCl, is obtained as an insoluble yellow 
powder by heating auric chloride to 230°. 

Auric chloride or trichloride of gold, AuCP, is prepared by 
dissolving the metal in aqua regia. After concentration the 
liquid solidifies, on cooling, to a dark-red, crystalline and deli- 
quescent mass. 

The solution of auric chloride is yellowish-brown when con- 
centrated, pure yellow when dilute. It is decomposed by light. 
It colors the skin violet, and is reduced by a great number of 
bodies. Phosphorus, and hypophosphorous, phosphorous and 
sulphurous acids precipitate from it metallic gold. It is the 
same with most of the metals, which combine with the chlorine, 
setting free the gold. A brown precipitate of metallic ^Id is 
immediately obtained on adding a solution of ferrous sulphate 
to a solution of auric chloride. Auric chloride dissolves in 
ether, which removes it from its aqueous solution when the 
two liquids are agitated together. 

If a solution of auric chloride be added to a mixture of 
stannous and stannic chlorides in solution, a flocculent precipi- 



376 ELEMENTS OF MODERN CHEMISTRY. 

tate of a purple color, more or less pure according to the con- 
centration of the solutions and the proportions of the mixture, 
will be formed. It is purple of Oassius, a compound employed 
in painting on glass and porcelain. It contains tin, gold, oxy- . 
gen, and hydrogen, but its constitution is not well known. 

Auric chloride forms crystalline compounds with the alkaline 
chlorides. When a mixture of chloride of gold and sodium 
chloride is evaporated until a pellicle forms on its surface, yellow 
crystals containing NaCl. AuCP -|- 2H^0, are formed on cooling. 

Gilding'. — Several processes are used for gilding metals, such 
as silver and copper. The objects may be gilded by amalga- 
mation, or by galvanic deposition. 

Gilding hy Amalgamation. — Grold readily alloys with mer- 
cury, and the amalgam is used for gilding objects of silver and 
copper. The pieces are heated to destroy greasy matters, and 
are then cleaned by dipping them into dilute sulphuric acid, 
after which they are washed and dried with saw-dust. They 
are then rubbed with a brush of brass wires dipped into a solu- 
tion of mercurous nitrate, and then with a brush impregnated 
with an amalgam of one part of gold and eight parts of mer- 
cury. They are afterwards heated to volatilize the mercury, 
an operation dangerous to the health of the workmen, and 
which should be conducted in a furnace having a good draught. 
The pieces thus gilded are dull; they become lustrous after 
suitable washings and polishings. 

Electro- Gilding. — The copper objects, previously heated and 
cleaned by dilute sulphuric acid, are plunged for a few seconds 
into dilute nitric acid and then wiped dry. They are then 
connected with the negative pole of a battery and dipped into 
a bath composed of 1 part of cyanide of gold, 10 parts of potas- 
sium cyanide, and 100 parts of water. A plate of gold plunged 
into the same bath constitutes the positive pole. When the 
current passes, the objects become covered with a uniform and 
adherent coating of gold. As the metal is precipitated from 
the solution, it is replaced by an equivalent quantity from that 
whic]^ constitutes the positive pole, and which dissolves. The 
bath thus retains a constant composition. The same process 
is applicable to electro-silvering. 

Assaying of Gold Alloys. — Gold i-s assayed by cupellation. 
The alloy is first melted with silver, so that the quantity of the 
latter metal present may be at least triple that of the gold. 
This alloy is submitted to cupellation, an operation which 



BISMUTH. 377 

presents no difficulty, for silver rich in gold does not spit. 
The button is hammered out to a thin sheet, reheated and 
formed into a little cornet, which is introduced into a small 
flask and heated with nitric acid of 22° Baume. After several 
minutes' boiling the greater part of the silver is dissolved ; the 
liquid is then decanted and replaced by more concentrated nitric 
acid. All of the silver dissolves and the gold remains in the 
form of a but slightly coherent cornet. It is washed, heated to 
redness in a crucible to give it coherence, and finally weighed. 



BISMUTH. 

Bi = 206.54 

Extraction. — This metal is found native in a quartzy gangue. 
It is extracted by simply heating the mineral in cast or sheet 
iron tubes, which are arranged in an inclined position in a fur- 
nace. The bismuth melts and runs out at an opening in the 
lower end of the tubes. 

The bismuth of commerce is never pure ; it contains traces 
of other metals, nearly always of arsenic and sometimes of 
sulphur. It is purified by pulverizing it, mixing it with 2V 
its weight of potassium nitrate, and heating the mixture to 
redness in a clay crucible. The foreign metals more oxidiza- 
ble than the bismuth are thus converted into oxides, the ar- 
senic into arsenate of potassium, and the sulphur into potassium 
sulphate. This treatment may be repeated a second time if 
necessary. 

Properties. — Bismuth is a whitish-gray metal, having a 
reddish tinge. Its fracture is crystalline and laminated. Its 
density is 9.83, and it melts at 264°. On cooling, it crystal- 
lizes in rhombohedra, of which the surfaces become covered 
with a thin film of oxide, causing a beautiful iridescent play 
of colors like that on a soap-bubble. 

Bismuth increases in volume on solidifying. It volatilizes at 
a white heat. It is unaltered by the air at ordinary tempera- 
tures, but at a red heat it absorbs oxygen and burns, formiag 
bismuth oxide. Its best solvent is nitric acid, which converts 
it into nitrate. 

The various compounds of bismuth present great analogy to 
those of antimony, next to which this metal might be placed 
in the group including nitrogen, phosphorus, arsenic, antimony, 
and bismuth. 

32* 



378 ELEMENTS OF MODERN CHEMISTRY. 

This analogy is shown in the following synoptic table : 
BiCP SbCP 

Bismuth trichloride. Antimony trichloride. 

Bismuth trioxide. • Antimony trioxide. 

Bi^O^ Sb^O^ 

Bismuthic anhydride. Antimonic anhydride. 

I Bi^O* Sb^O* 

II Bismuth bismuthate. Antimony antimonate. 

■' Bi^S^ Sb^S^ 

Bismuth trisulphide. Antimony trisulphide. 

Otherwise, bismuth is related to the metals proper, not only 
by its properties, but by the facility with which it forms defi- 
nite salts. It is triatomic in its more important combinations, 
the oxide, chloride, and nitrate. 



BISMUTH TRIOXIDE. 

Bi203 

This body is obtained by decomposing the nitrate by heat. 
It is a straw-yellow powder, fusible at a red heat, and yielding 
on cooling a dark-yellow, vitreous mass. It attacks clay cruci- 
bles even more rapidly than litharge. 

A hydroxide of bismuth is formed when the nitrate or sub- 
nitrate is treated with potassium hydroxide or ammonia. It 
is a white powder, insoluble in an excess of alkali, and when 
boiled with caustic potash it is converted into the crystalline 
anhydrous oxide. 

BISMUTH TRICHLOmDE. 

BiC13 

Finely-divided bismuth will burn in chlorine, being con- 
verted into chloride. The latter is prepared by directing a 
current of chlorine upon melted bismuth contained in a retort. 
The chloride distils and solidifies in the receiver to a fusible, 
crystalline, and deliquescent mass, formerly known as butter 
of bismuth. A crystallized, hydrated chloride of bismuth may 
also be obtained by evaporating a solution of bismuth in nitro- 
hydrochloric acid. 

Bismuth chloride dissolves in water charged with hydro- 
chloric acid, but is decomposed when treated with pure water j 



BISMUTH NITRATE. 379 

in the latter case an oxychloride is formed and precipitated as 
a fine, white powder, hydrochloric acid being at the same time 
formed. 

2BiCP + 2H^0 = 2BiOCl + 4HC1 

Bismuth oxychloride is known as pearl-white. It contains 
BiOCl. 

BISMUTH NITBATB. 

Bi(N03)3 

Bismuth dissolves readily in nitric acid, and the concentrated 
solution deposits large, four-sided prisms, which are colorless 
and deliquescent. They contain Bi(N0'7 -j- 3H^0. They 
are very soluble in water acidulated with nitric acid, but if this 
solution be poured into a large excess of water, a pulverulent, 
white precipitate is formed, and increases in volume if very 
dilute ammonia be gradually added to the liquid in order to 
partly neutralize the free acid. 

This precipitate is much employed in medicine in cases of 
chronic diarrhoea under the name of subnitrate of bismuth. 
Its composition is generally expressed by the formula BiNO* 
4- H^O = (BiO)'NO^ -f WO. 

It may be regarded as bismuthyl nitrate, that is, nitric 
acid, HNO^ in which the monobasic atom of hydrogen is re- 
placed by the monatomic group BiO. Or it may be considered 
as a derivative of orthonitric acid, H^NO*, corresponding to 
orthophosphoric acid, H^PO* (page 191). 

Boiling water removes still more nitric acid from this sub- 
nitrate, leaving a residue, which is used as a cosmetic, known as 
hlanc de fard. 

Characters of Solutions of Bismuth. — When mixed with 
k large quantity of water, bismuth solutions give white pre- 
cipitates of sub-salts. Hydrogen sulphide, and the soluble 
sulphides form a brown precipitate of bismuth sulphide, insolu- 
ble in an excess of ammonium sulphide. The alkaline hydrox- 
ides and carbonates give white precipitates, insoluble in an 
excess of the reagent. 

Bismuth solutions are not precipitated by either sulphuric 
or hydrochloric acid. 

When heated with sodium carbonate in the reducing flame of 
the blow-pipe, compounds of bismuth yield a metallic globule, 
very brittle after cooling. 



380 ELEMENTS OF MODERN CHEMISTRY. 

The following elements, from aluminium to manganese, form 
series of compounds in which they must be regarded as tri- 
atomic. In these compounds a single atom of the metal is 
united with three monatomic atoms or radicals, or two such 
atoms act as a hexatomic couple (R^)""'. The chlorides may 
consequently present either the general formula RCP or E.^CP, 
while the oxides are represented by R^O^ In addition, iron, 
nickel, cobalt, and manganese form compounds in which the 
metal appears to be diatomic ; as, for example, iron in ferrous 
oxide, FeO, and ferrous sulphate, FeSO*. The oxides of this 
latter class are strongly basic ; the sesquioxides are also basic, 
but in the presence of more energetic bases may act as weak 
acids. Iron and manganese also form oxides of the composi- 
tion FeO^ and MnO'^, which act as the anhydrides of acids. 



ALUMmiUM. 

Al = 26.91 

This metal long remained a chemical curiosity, and has only 
become common within a few years. It was discovered in 
1827 by Wohler, and in 1854, H. Saint-Claire Deville suc- 
ceeded in producing it on a large scale by decomposing alu- 
minium and sodium double chloride by sodium. 

2AlCP,NaCl + 6Na = 8NaCl + 2A1 

Aluminium is now produced most cheaply by the processes 
of Hall and Heroult. They consist in the electrolytic de- 
composition of alumina, APO'^ dissolved in a bath of fused 
cryolite, AlFlSNaF. The latter is melted by the heat of the 
electric arc, and alumina constantly added while a powerful 
current is passing through the mass. The oxygen disen- 
gaged combines with the carbon forming the anode, and the 
aluminium collects upon the hearth, which serves as the 
cathode. The process is continuous : fresh alumina is con- 
stantly added to keep the bath saturated with it, and the 
furnace is tapped periodically. 

Aluminium of a high degree of purity is obtained in this 
manner. 

Aluminium is a white metal, with a somewhat bluish lustre 
when polished. It is ductile, malleable, very sonorous, and a 
good conductor of heat and electricity. It is as light as glass 



ALUMINIUM OXIDE — ALUMINIUM CHLORIDE. 381 

and porcelain, its density being only 2.56. It melts at 700°, 
and is not volatile. 

Aluminium is unaltered by the air, even by moist air. Wben 
heated in tliin sheets in a current of oxygen, it burns and is 
converted into alumina. Nitric and sulphuric acids scarcely 
attack it. Hydrochloric acid dissolves it rapidly, disengaging 
hydrogen. It is immediately attacked by boiling solutions of 
potassium or sodium hydroxide ; hydrogen is disengaged and 
alkaline aluminates are formed. 

ALUMINIUM OXIDE, OR ALUMINA. 

AP03 

Corundum^ a very hard precious stone, consists of anhydrous 
alumina. It is named oriental ruby when it has a red color ; 
sapphire when it is blue, and oriental topaz when it has a 
yellow tint. Emery is a sort of opaque corundum ; it is gran- 
ular and colored by a small quantity of oxide of iron. 

When ammonium carbonate is added to a solution of alum, 
carbon dioxide is evolved, and a gelatinous precipitate of hy- 
drated alumina is formed. 

The precipitate dissolves readily in caustic potash. When 
heated, it loses water and is converted into anhydrous alu- 
mina; the latter is fusible only in the flame of the oxyhydro- 
gen blow-pipe and in the electric furnace. It assumes crys- 
talline structure upon solidifying. 

Some of the precious stones above mentioned have been 
produced artificially by melting alumina with various fluxes 
and minute quantities of coloring matters (Gaudin, Fremy). 

Alumina is reduced by carbon only at the high tempera- 
ture of the electric furnace, but it readily yields to the joint 
action of carbon and chlorine, and is converted into aluminium 
chloride. 

ALUMINIUM CHLORIDE. 
AlCF or AFCP 

When a current of chlorine is passed over an incandescent 
mixture of alumina and charcoal, aluminium chloride and 
carbon monoxide are formed (Oersted). 

APO' + 3C -f 3CP = SCO + 2A1CP 

Aluminium chloride thus formed is a white, crystalline sub- 
stance, sometimes having a light-yellow color. It is fusible, and 



382 ELEMENTS OF MODERN CHEMISTRY. 

volatilizes in tlie air at a temperature little above 100°. When 
exposed to the air it gives oiF white fumes and attracts moist- 
ure. It dissolves in water with production of heat. 

A solution of aluminium chloride may be obtained by dis- 
solving gelatinous alumina in hydrochloric acid. When this 
solution is evaporated, it decomposes as soon as it attains a 
certain degree of concentration, disengaging hydrochloric acid, 
and leaving alumina. 

Aluminium chloride readily combines with sodium chloride, 
forming a double chloride, AlCP.NaCl, fusible towards 200°. 

ALUMINIUM SULPHATE. 

A12(SO*)3 -f 18H20 

This is obtained in the arts by decomposing non-ferruginous 
clays with sulphuric acid. It crystallizes with difficulty in 
needles and in thin, pearly scales. In this state it contains 18 
molecules of water of crystallization. It dissolves in 2 parts 
of cold water. When heated, it first loses its water, and at a 
higher temperature it gives off sulphuric anhydride, leaving a 
residue of alumina. 

AP(SO*)^ = 3S0^ + APO^ 

It is seen that aluminium sulphate represents 3 molecules 
of sulphuric acid, in which the 6 atoms of hydrogen have been 
replaced by the hexatomic couple AP. 

H^SO*^ (SO* 

H^SO* [ + APO^ = BH^O + (AP)-^ ] SO* 
H^SO*) (so* 

ALUMINIUM AND POTASSIUM DOUBLE SUL- 
PHATE, OR ALUM. 

A12(S04)3.K2S04 -f 24H20 

If a concentrated solution of aluminium sulphate be added 
to a concentrated solution of potassium sulphate, and the mix- 
ture be stirred with a glass rod, a crystalline deposit soon forms 
from the union of the two salts to form a double sulphate 
which is alum. 

This salt is not very soluble in cold water, but dissolves 
abundantly in boiling water, and is deposited on cooling in 



ALUM. 383 

voluminous, transparent octaliedra. When heated, these crys- 
tals melt in their water of crystallization (24 molecules), and 
in losing this water, the melted mass swells up considerably. 
Alum may be obtained crystallized in cubes, and it is prepared 
in this form in the neighborhood of Civita-Yecchia by working 
a mineral which contains the elements of alum with a large 
excess of alumina. The mineral is known as alumimte, and the 
cubical alum is called Roman alum. 

This cubical variety may be prepared in the laboratory by 
adding a small quantity of potassium carbonate to a hot solu- 
tion of ordinary alum, so that the precipitate first formed will 
be redissolved on agitating the liquid. On cooling, cubical 
crystals are deposited which are ordinarily opaque. These are 
formed under the influence of a small quantity of basic sul- 
phate (aluminium sulphate combined with an excess of alu- 
mina) contained in the liquid, and which probably enters into 
the constitution of the crystals. With this slight difference, 
octahedral alum and cubical alum present the same composi- 
tion, which is expressed by the formula AP(SO*)lK'SO* + 
24H^O. 

Ammonia alum is obtained by adding ammonium sulphate 
to solution of aluminium sulphate. It possesses a constitution 
analogous to that of ordinary alum, with which it is isomor- 
phous. It contains 

AP(SO^)l(NH0'SO* + 24H^O 

It is often substituted in the arts for potassium alum, being 
cheaper than the latter. 

When strongly calcined, it leaves a residue of pure alumina. 

Other alums are known in which iron, manganese, and chro- 
mium play the part taken by aluminium in ordinary alum.. 
These alums are all isomorphous (Mitscherlich). By the ac- 
tion of sulphuric acid on the sesquioxides of the above metals, 
sulphates are formed analogous to aluminium sulphate, and of 
which the composition is expressed by the general formula 
(R')^'(SOO'. With the sulphates W^0\ they form alums, all 
of which crystallize in regular octahedra, and which can be 
mixed in one and the same crystal without the form of the 
latter being affected by the mixture. 

The following are the most important of these compounds : 

Manganese alum .... Mn2(SO*)3.K2SO^ + 24H20 

Iron alum Fe2(SO*)3.K2S04 + 24H20 

Chromium alum .... Cr2(S0*)3.K2S0* + 24H20 



384 ELEMENTS OP MODERN CHEMISTRY. 

It is seen that eacli of tliese presents an atomic composition 
similar to that of ordinary alum. 



The aluminium compounds are widely disseminated in nature. 
Feldspar^ or orthodase, is a double silicate of aluminium and 
potassium. The latter metal is replaced by sodium in alhite, 
and by calcium in anortliite and lahradorite. 

Many other minerals contain aluminium silicate combined 
with alkaline or earthy silicates : such are leucite, garnet, 
idocrase, mica, etc. The zeolites are silicates of aluminium 
containing water of crystallization. 

Clay is a hydrated silicate of aluminium ; it results from the 
disintegration of feldspar by the action of water and air, the 
alkaline silicate being gradually dissolved and eliminated. The 
purest clay is kaolin, or porcelain clay ; it contains alumina, 
silica, and water in the proportions indicated by the formula 
2SiO^AP0^2H•^0. 

Plastic clays are those which form a binding paste when 
mixed with water, and acquire great hardness after being 
baked, without fusing. They are used for the manufacture of 
pottery, refractory fire-bricks, and crucibles. Fuller s earth is 
a clay which forms with water a paste that is but slightly adhe- 
rent ; it is employed in scouring and fulling cloth. 

Marls are intimate mixtures of clay and chalk ; they are 
employed in agriculture. 

Pottery. — Clay is the basis of all pottery. Other matters, 
such as sand, powdered feldspar or quartz, etc., are generally 
added, for while they diminish the plasticity of the clay, they 
also diminish its shrinkage on baking. Pottery is classified as 
semivitrified pottery, such as porcelain and stoneware ; porous 
pottery, such as faience and bisque; and common pottery or 
terra-cotta. 

Porcelains. — These are manufactured from kaolin, to which 
sand is added to prevent shrinkage, and feldspar, which causes 
the ware to undergo a partial fusion, and renders it translucent. 
These materials are finely pulverized, mixed with water, and 
the paste is kneaded for a long time in order to render it homo- 
geneous. Pieces fashioned in this paste are submitted to a pre- 
liminary baking, which gives them a certain degree of coherence. 
The porous porcelain thus obtained must be coated with a var- 
nish which will melt and spread upon its surface : this glaze is 



CERIUM, LANTHANUM, AND DIDYMIUM. 385 

formed of a mixture of quartz and kaolin reduced to an impal- 
pable powder ; the latter is suspended in water, into whicli tlie 
pieces are dipped. They are then subjected to a second baking 
in ovens where the temperature is sufficiently elevated to fuse 
the glaze and partially vitrify the paste. 

Ceramic Stonewares. — These are manufactured from the 
same materials as porcelain, but less pure ; they are therefore 
slightly colored. They are baked at a high temperature, and 
are glazed by throwing common salt upon the incandescent, 
objects in the furnace ; hydrochloric acid is disengaged, and a 
double silicate of aluminium and sodium is formed, which fuses 
and spreads upon the surface of the ware. 

Faiences are made from plastic clay mixed with quartz re- 
duced to an impalpable powder. Articles formed of this paste 
are submitted to a preliminary baking, and are then coated with 
a fusible glaze, composed of quartz, potassium carbonate, and 
oxide of lead. A second baking causes the pieces to become 
covered with an impermeable, vitreous layer of silicate of lead 
and potassium. This glaze is transparent ; for ordinary ware 
it is rendered opaque by the addition of oxide of tin. It is 
a true enamel. 

Common pottery^ which serves for culinary purposes, is made 
from ferruginous clay, mixed with sand and marl. The glazing 
is composed of a double silicate of aluminium and lead. 



CEEIUM, LANTHANUM, AND DIDY- 
MIUM. 

These rare metals are found associated as silicates in the 
mineral cerite^ and as phosphates in monazite. Their separa- 
tion is a matter of some difficulty. The mineral is treated 
with sulphuric acid, by the aid of heat, and the solution ob- 
tained after filtering from the separated silica is precipitated 
by ammonium oxalate. A mixture of the oxides is obtained 
when the oxalates are calcined : these oxides are converted 
into nitrates and these again into double nitrates with am- 
monium nitrate. By repeated and systematic fractional crys- 
tallization a clean separation of the elements is effected. The 
same process also serves to break up didymium, long supposed 
to be an element, into its components, neodymium 2jidi praseo- 
dymium (Auer V. Welsbach). 
■R z 33 



386 ELEMENTS OP MODERN CHEMISTRY. 

The metals have been isolated by decomposing their chlorides 
by electricity. 

They possess about the hardness of lead, and a color and lustre 
resembling iron : didymium is rather more yellow. Their den- 
sity is comprised between 6.05, that of lanthanum, and 6.7, of 
cerium. They are readily oxidised, and burn brilliantly when 
heated in the air. 

The cerium metals are triatomic, cerium itself also tetra- 
tomic. It forms the oxides Ce'^O^ and CeO^ Lanthanum 
oxide has the composition La'^0^ ; neodymium oxide is Nd'^0^, 
while praseodymium forms two oxides, Pr^O^ and Pr*0^ The 
chlorides correspond to the formula RCP. The cerous com- 
pounds are mostly colorless ; eerie compounds are yellow. 
Lanthanum salts are colorless, while the pink color of didy- 
mium salts is the resultant of a mixture of reddish-violet 
(neodymium) and apple-green (praseodymium). 

The oxides of lanthanum and cerium, as well as several 
other oxides (zirconia, thoria), are employed in the Welsbach 
burner, in which a fine gauze cylinder of such oxides is ren- 
dered incandescent by the heat of a non-luminous gas-flame. 



GALLIUM. 

Ga = 69.9 

In 1869, Mendelejeff predicted the existence of an unknown 
metal whose chemical relations should resemble those of alumin- 
ium, and whose atomic weight should be about 70. In 1876, 
Lecoq de Boisbaudran, while pursuing spectroscopic investiga- 
tions, and in a line of research very different from that of Men- 
delejeff, discovered the missing element in a zinc blende. Since 
then it has been found in small quantity in many blendes : one 
of the richest, found in Westphalia, contains only one sixty- 
thousandth of its weight. 

In order to extract the gallium, the ore is roasted, and the 
product dissolved in sulphuric acid. An acid liquor is thus 
obtained, containing principally sulphate of zinc, with sulphates 
of iron, aluminium, indium, etc., and a trace of gallium sul- 
phate. 

The following reactions are employed by Lecoq de Bois- 
baudran and Jungfleisch for the separation of the gallium : 



INDIUM. 387 

1. When the liquid is neutralized, the ferric oxide, alumina, 
and gallium oxide, which is a sesquioxide, are precipitated. 
The precipitate is redissolved in sulphuric acid, and the same 
operation repeated after converting the ferric oxide into ferrous 
oxide, which remains dissolved in the neutral liquid. By this 
means the greater part of the iron is removed. 

2. Gallium oxide dissolves, like alumina and zinc oxide, in 
an excess of potassium hydrate ; when this solution is saturated 
with hydrogen sulphide, the zinc is precipitated as sulphide, 
while tne gallium and aluminium remain in solution. The 
gTeater part of the zinc is thus separated. 

3. When water is added to a boiling solution of gallium 
sulphate, the latter is precipitated as subsulphate, while alumi- 
nium sulphate remains in solution. 

4. Gallium oxide dissolves in an excess of ammonia ; alumina 
does not. 

5. Gallium separates in the metallic state when a voltaic 
current is passed through an alkaline solution of gallium oxide. 

Physical Properties. — Gallium has a metallic lustre recalling 
that of nickel. It readily crystallizes in forms derived from a 
right rhombic octahedron, generally in magnificent laminae. Its 
density is 5.96. It melts at 29.5°, and has a tendency to re- 
main in a state of superfusion. It is not volatile. 

This collection of properties gives to gallium a special place 
among the metals. 

Chemical Properties. — These are but little known at present. 
Gallium is oxidized but little, if at all, when heated in the air 
or in oxygen. It forms a sesquioxide, Ga^O^, which resembles 
alumina in that it forms alums. Gallium alum was obtained 
by Lecoq de Boisbaudran. 

Gallium combines directly with chlorine, forming a solid, 
crystalline, and very volatile chloride. 



i:^DIUM. 

In = 113.4 



This metal was discovered in 1863 by Reich and Richter 
in the zinc blendes of Freiberg (Saxony). It appears to exist 
in the majority of zinc blendes, and accompanies the zinc which 



388 ELEMENTS OF MODERN CHEMISTRY. 

is extracted from those minerals. It is ordinarily obtained 
from commercial zinc, which, however, contains only very 
small quantities of it. 

Indium is a brilliant metal, possessing almost the lustre of 
silver. It is soft and ductile. It melts at 176°, and is vola- 
tile, but less so than zinc and cadmium. It approaches these 
metals in its general chemical properties, but is more electro- 
negative, both of the latter metals precipitating it from its 
solutions. Its position in the periodic system relates it to gal- 
lium and aluminium on the one hand, and to zinc and cad- 
mium on the other. 

Indium is characterized by several spectroscopic lines, 
among which are a very brilliant blue and a less marked vio- 
let line. 

Two oxides of indium have been described, a sesquioxide, 
ln'^0^, and a suboxide, InO. The first is obtained by cal- 
cining the nitrate ; it is yellow. When heated to 300° in a 
current of hydrogen, it is partially reduced, yielding a black 
suboxide. 

Indium chloride, InCP, is formed when indium is heated 
in a current of chlorine. It is a snow-white, volatile solid. 

Like aluminium and gallium, indium forms double sul- 
phates, or alums ; the ammonium double sulphate has the 
composition InXS0*)l(NH^)2S0* + 24:WO. 



RAEE EAETHS. 

In 1794, Gadolin, a Finn, discovered in the mineral gado- 
linite, which bears his name, an oxide, which was named yttria. 
In 1843, Mosander concluded from researches on this earth 
that it contained at least three oxides, the metallic radicals of 
which were introduced into the list of elements under the 
names erbium, terbium, and ytterbium or yttrium. 

Until recently little was known concerning these oxides, but 
the investigations of Crookes, Delafontaine. Lawrence Smith, 
Marignac, Cleve, and Nilson have shown that the earths 
formerly known as erbia and yttria are much more complex 
than was supposed. The oxides of at least six metals have 
been isolated, and it is possible that the series may be com- 
pleted by the separation of others. 



IRON. 389 

These elements exist in gadoUnite, euxenite, orthite, thorite, 
and particularly in the samarsJcite of North Carolina, in which 
they occur as niobates and tantalates. Their quantity is so 
small, and the separation of their oxides is attended with such 
difficulties, that, excepting yttrium, the elements have not 
yet been isolated. Their oxides, and in some cases a number 
of salts, have been examined, and spectroscopic analysis has 
aided in setting aside all doubt as to the existence of the 
elements. 

The following atomic weights of these elements are calcu- 
lated to agree with the formula B.^0^ for the oxides : 

Scandium, discovered by Nilson and studied by Clave, bas an atomic 
weight of about 44; the oxide is white. The existence of scandium was 
predicted by Mendelejeff under the name ekaboron. 

Samarium. — Atomic weight = 149. This element was named by Lecoq 
de Boisboudran, and appears to be identical with decipium, of which Dela- 
fontaine announced the existence in 1878; its oxide is white. 

Holmium. — Atomic weight about 162 (Cleve). 

Erbium. — Atomic weight = 166 ; forms a pink oxide and rose-colored 
salts (Cleve). 

Thulium. — Atomic weight = 170.4 ; a white oxide. 

Yttrium. — Atomic weight = 89.6. The metal has been prepared by 
electrolysis of the chloride, and also by reduction of the latter by sodium 
and magnesium. It is a gray powder. Yttria is a white oxide. 

Ytterbium. — Atomic weight = 172.6. 



IROK 

Fe (Ferrum) = 55.60 

Natural State and Metallurgy. — Iron is the most impor- 
tant of the metals. Its preparation and working are- difficult, 
therefore it was not the first metal used by civilized man. The 
bronze age preceded the iron age, and those who first employed 
the latter metal probably extracted it from the masses which 
fall from time to time upon the surface of the earth, and are 
known as meteorites. Their principal constituent is metallic 
iron, which is alloyed with nickel, cobalt, and chromium. 

Iron is employed in three principal forms : soft or malleable 
iron, cast iron, and steel. Soft iron is almost pure iron ; cast 
iron is a combination of iron with carbon and silicon ; steel 
also contains carbon, but in smaller proportion than cast iron. 

The principal ores of iron are the magnetic, or black oxide, 
33* 



390 



ELEMENTS OF MODERN CHEMISTRY. 



Fe^O*, red hematite, Fe^O^, and spathic iron or ferrous carbon- 
ate, FeCO^. The various hydrates of the sesquioxide {^oolitic 
iron, brown hematite, etc.) and ferrous carbonate mixed with 
clay (bog-iron ore), are more abundant than the preceding, but 
are not as rich and are less valuable. 

All of these minerals are oxidized. If the ore contain sul- 
phur, that element is first driven out by roasting. The metal- 
lurgy of iron then consists in reducing the oxide with carbon, 
and separating the reduced iron from the earthy matter, which 
is generally silicious. Two methods are employed for this 
purpose. The first consists in heating the rich ores with 
charcoal alone ; part of the oxide of iron then combines with 
the gangue, forming a very fusible slag (double silicate of 
aluminium and iron). This is the Catalan method. The 
other consists in mixing the ore with coal and calcium carbon- 
ate ; the gangue then com- 
bines with the lime, forming 
a double silicate of lime and 
aluminium, which fuses only 
at a very high temperature. 
Under these conditions the 
iron unites with a portion 
of the carbon, forming cast 
iron. This is the blast-fur- 
nace method. 

Catalan Method. — This is 
only applicable to very rich 
ores and in countries where 
combustibles are expensive, 
as in Spain, the Pyrenees, 
and in Corsica. 

Fig. 116 represents a sec- 
tion of a Catalan furnace ; it 
is a trough-shaped masonry 
furnace with a hearth. The 
materials are jDlaced in two 
piles, side by side, upon a layer of well-ignited charcoal ; one pile 
consists of charcoal and is next the tuyere ; the other is the 
ore, equal to half the quantity of charcoal, and is placed oppo- 
site. The combustion is sustained by the blast from a tuyere, 
D, which reaches the border of the hearth. The carbon 
dioxide here formed is converted into carbon monoxide by the 




Fig. 116. 



IRON, 



391 



mass of incandescent charcoal, and the latter gas reduces the 
ore, again passing into the state of dioxide. Metallic iron is 
thus formed, and at the same time a portion of the ferric 
oxide is reduced to ferrous oxide, and combines with the 
gangue, forming a double, alumino-ferrous silicate, which is very 
fiisible and constitutes the slag. The reduced iron collects in 
the bottom of the hearth in the form of a spongy mass, which 
is agglutinated and forged under the hammer. 




Fig. 117. 



Blast-furnace Process. — All iron ores may be treated by this 
method. They are crushed and introduced with alternate 
layers of limestone and coal into the blast-furnace (Fig. 117). 
The latter has the form of two cones, the bases of which axe 



392 ELEMENTS OF MODERN CHEMISTRY. 

joined together. It is closed at the bottom, and hot air is in- 
jected through tuyeres to sustain the combustion. It is open at 
the top, where it is continually charged with fresh materials, as 
the incandescent mass sinks in the furnace and the molten mate- 
rials are drawn off below. The latter first collect in a cavity 
placed below the vent of the tuyere, and separate on this 
hearth into metal, which sinks to the bottom, and slag, which 
floats and is drawn off periodically through an opening called 
the slag-hole. When the crucible is full of molten metal, the 
latter is run off into channels made in sand upon the floor of 
the casting-room. In these rough moulds it solidifies in bars 
having a semicircular section, which are called pz^s. 

The reactions which take place in the blast-furnace are of 
great interest. At the lower part, where the temperature is 
the highest, carbon dioxide is produced by the combustion of 
the coal ; farther up, in the widest portion, this gas is reduced 
to carbon monoxide by the incandescent coal ; still higher, 
where the furnace begins again to contract, and where the 
temperature is dull red, the carbon monoxide reduces the oxide 
of iron, and a spongy mass of metallic iron is there formed. 

In descending, this iron unites with part of the carbon, and 
at the same time the silica of the gangue combines with the 
lime, forming a silicate which fuses and constitutes the slag. 

A small quantity of silica is reduced in the hottest part of 
the furnace, and the silicon formed combines with the cast iron. 

Cast iron is converted into soft iron by refining ; this opera- 
tion consists in removing from the cast iron the greater part 
of its carbon. For this purpose it is melted in contact with 
the air ; the carbon, silicon, and a small proportion of iron are 
oxidized, forming a basic silicate, of which the excess of oxide 
is finally reduced by the carbon of the cast iron. The latter 
thus becomes less fusible, and is converted into a spongy mass 
of soft iron. Several of these masses are united and the scoriae 
expressed from them by the blows of a steam-hammer. Or the 
metal is melted on the hearth of a reverberatory furnace under 
a layer of ferruginous scoriae and scales of oxide of iron ; the 
oxygen of these materials burns the carbon out of the cast iron, 
the whole mass being vigorously stirred. The latter operation 
is called puddling. 

Preparation of Pure Iron. — Pure iron may be obtained by 
reducing ferric oxide by hydrogen at a temperature near red- 
ness, or by passing hydrogen over anhydrous ferrous chloride 



IRON. 393 

contained in an incandescent porcelain tube. Hydrochloric 
acid is formed and evolved, and the iron remains as a gray, 
spongy mass, having a metallic lustre where it has been in 
contact with the porcelain (Peligot). 

Properties of Soft Iron. — Forged or bar iron is not pure. 
It contains a small quantity of carbon, and traces of silicon, sul- 
phur, phosphorus, and even nitrogen. The purest soft iron is 
that used for the teeth of carding-machines and for piano-strings. 

The density of forged iron varies from 7.4 to 7.9. It is 
very tenacious, ductile, and malleable. When rolled out, it is 
called sheet iron. Tin plate is sheet iron covered with a layer 
of tin. Galvanized iron is coated with a surface of zinc. 

Iron melts only at the highest heats of a wind-furnace. 
When softened by a white heat, it may be soldered to itself, or 
welded, a very important property for the working of the metal. 

0.05 per cent, of aluminium greatly lowers the melting point 
of iron, so that the presence of this quantity of aluminium per- 
mits iron castings to be made that otherwise would be impos- 
sible. They are called mitis castings. 

Iron is attracted by tho, magnet ; it is magnetic ; but it is 
not, like steel, capable of retaining magnetism when removed 
from the magnetic influence. 

It is not altered by dry air at ordinary temperatures, but at 
a red heat it absorbs oxygen and is converted into scales of black 
oxide of iron. Iron may be obtained as an impalpable powder 
by reducing finely-divided ferric oxide in a current of hydrogen 
at as low a temperature as possible. In this state it takes fire 
when exposed to air at ordinary temperatures : it is pyrophoric. 

Iron rapidly becomes oxidized in moist air ; it becomes cov- 
ered with a layer of rust, which is ferric hydroxide. It is con- 
sidered that the oxidation of iron moistened with water is first 
set up by the oxygen dissolved in the water ; it continues with 
greater energy as soon as a light coat of ferric hydroxide has 
been formed on the metal. The hydroxide forms a voltaic 
couple with the iron itself, by which the water is decomposed ; 
part of the hydrogen displaced by the iron combines with the 
nitrogen of the air, forming ammonia; indeed, rust always 
contains a small proportion of ammonia. 

Iron decomposes water at a red heat, setting free the hydro- 
gen. It dissolves readily in hydrochloric acid, liberating impure 
and fetid hydrogen. If dilute nitric acid be poured upon iron 
tacks, the metal is at once attacked, with an abundant disen- 
gagement of red vapors. 



394 ELEMENTS OF MODERN CHEMISTRY. 

On the other hand, the metal is not attacked by concen- 
trated nitric acid (sp. g. 1.45). After having been immersed 
in the strong acid, it may be put into dilute acid, and the 
latter will have no effect upon it. By the action of the con- 
centrated acid (other oxidizing agents act in a similar manner) 
the iron has become passive : its surface is covered with a thin 
film of oxide which protects it. If now it be touched with a 
copper wire while in the dilute acid, the protecting film is 
ruptured and chemical action promptly re-established. 

Cast Iron and Steel. — The properties and appearance of cast 
iron differ with the proportions of carbon and silicon which it 
contains. These elements appear to exist in the iron in a 
number of forms ; they are partly in combination with the 
metal and partly only dissolved by it when it is liquid. When 
cast iron containing much carbon is quickly cooled, it becomes 
hard, brittle, whiter than soft iron, and seems homogeneous. 
This is white iron. When slowly cooled, a large proportion 
of the carbon is deposited as laminae of graphite, and the less 
homogeneous iron then possesses a certain degree of mallea- 
bility : it is gray iron. 

Some cast irons contain sulphur and phosphorus, and re- 
main white even after very slow cooling. Others are lamellar 
and glittering ; they contain manganese and are rich in carbon 
(spiegeleisen and ferromanganese). 

The proportion of carbon contained in cast iron varies from 
2 to 5.5 per cent. Steel contains less carbon, from 0.7 to 2 
per cent. The quantities of carbon contained in steel and even 
in cast iron render it difficult to suppose that these products 
are veritable carbides of iron. 

Steel may be obtained by a partial decarbonization of cast 
iron, Manganiferous iron is especially applicable for this prep- 
aration. It is submitted to a partial refining, being maintained 
in the liquid state for some hours under a layer of scoriae rich 
in oxide of iron. A part of the carbon is burned out by the 
oxygen of this oxide : natural steel is thus obtained. 

Soft iron may be converted into steel. The operation is con- 
ducted in cases of refractory fire-clay, into which bars of iron, 
and charcoal-powder, mixed with a small quantity of ashes and 
common salt, are introduced in alternate layers. The bars being 
thus isolated in a bed of charcoal, the cases are closed and 
heated to redness in a furnace. The incandescent metal absorbs 
carbon, and at the termination of the operation is found con- 
verted into steel by cementation. 



IRON. 



395 



The most homogeneous and most valuable steel is cast steel. 
It is obtained by fusing crude steel in crucibles in a wind-fur. 
nace. 

Bessemer has introduced an important improvement in the 
manufacture of steel. His process, which bears his name, con- 
sists in adding variable quantities of a properly-constituted cast 
iron to molten and perfectly refined soft iron. 

In this process, the iron to be converted into steel is decar- 
bonized by a current of air which is forced through the molten 
metal by strong press- 
ure. The operation is 
conducted in an appa- 
ratus represented in 
Fig. 118, which is 
called the converter. It 
has an ovoid form, is 
constructed of strong 
plate iron, and is well- 
lined with refractory 
fire-bricks. It is ar- 
ranged on trunnions, so 
that an oscillating move- 
ment may be given to it. 
The air arrives under 
pressure by the tuyeres 
which open into the bot- 
tom of the converter. 
The latter is first filled 
with incandescent coke, 
which is brought into active combustion by the blast. When 
the interior of the converter is heated to whiteness, the coke 
is emptied out and replaced by the molten cast iron, the con- 
verter being inclined to prevent the entrance of the metal into 
the tuyeres. The blast is then again turned on, and the com- 
pressed air bubbling through the molten metal burns out all 
of the carbon. A flame of great brilliancy rushes from the 
orifice of the apparatus, and the aspect of this flame indicates 
precisely the progress of the operation and its termination. 
At this moment the apparatus is inclined, the blast arrested^ 
and a sufiicient quantity of melted spiegeleisen, a crystalline 
cast iron rich in carbon, is added to the now refined iron to 
convert the whole into steel. The steel is then run out into 
suitable moulds. 




Fig. 118. 



396 ELEMENTS OF MODERN CHEMISTRY. 

A lining of lime or magnesia is substituted for the fire-bricks 
when the iron to be converted into steel is rich in phosphorus. 
The latter is then carried into the slag as a phosphate. 

Steel is susceptible of a high polish, and, like malleable 
iron, it can be forged. At the temperature at which malleable 
iron becomes soft, steel melts. It becomes hard and brittle 
when it is suddenly cooled after having been heated to redness. 
This operation, which is called tempering, develops new quali- 
ties in the steel, — elasticity and hardness. It assumes these 
properties in different degrees, according to the rapidity of the 
cooling, and the difference between the temperature to which 
it has been heated and that to whi^h it is cooled. The greater 
this difference, and the more rapid th'^, cooling, the harder will 
the steel become. Slow cooling makes it soft and malleable. 

When tempered steel is heated, and allowed to cool slowly, 
it partly or entirely loses its hardness. It loses it entirely if 
it be heated to the temperature to which it was exposed before 
tempering. Its temper is drawn incompletely, that is, it re- 
tains a certain amount of hardness and elasticity, if it be re- 
heated to inferior temperatures. The qualities which it will 
assume after cooling may be predicted from the various tints 
developed on its surface during the heating. Each of these 
tints corresponds to a determined temperature. 

Straw-yellow corresponds to 220° 
Brown " 255° 

Light blue " 285-290° 

Indigo-blue " 295° 

Sea-green « 331° 

OXIDES OF lEON. 

Three oxides of iron are known: 

Ferrous oxide FeO 

Ferric oxide Fe^O^ 

Ferroso-ferric oxide Fe^O* 

Fremy discovered the existence of a ferric acid, of which 
the composition is not certainly established. 

Ferrous Oxide, FeO. — Debray obtained this oxide by heat- 
ing ferric oxide in a current of gas formed of equal volumes 
of carbon monoxide and carbon dioxide. Ferrous oxide re- 
mains as a black powder. 

Fe^O^ + CO =: 2FeO + CO' 
Ferrous hydroxide^ Fe(OH)^, is formed as a white precipi- 
tate when an alkaline hydroxide is added to the solution of 



OXIDES OF IRON. 397 

a ferrous salt. In presence of air it absorbs oxygen rapidly 
and becomes dark in color. 

Ferric Oxide, Fe^Ol — This is found anhydrous in nature 
in red hematite and specular iron. It may be prepared by 
calcining ferrous sulphate, or green vitriol. This salt first 
loses its water, and then at a red heat decomposes into sul- 
phuric anhydride, sulphurous oxide, and ferric oxide. 

2FeS0* = SO^ + SO^ + ¥e'0' 

A red powder is thus obtained, which is known as colcothar, 
or jeweller's rouge. 

This oxide is amorphous, while red hematite is crystallized in 
acute rhombohedra. H. Deville has succeeded in converting 
the amorphous oxide into the crystallized by heating the former 
to redness in a very slow current of hydrochloric acid. 

Kust is ferric hydroxide, a combination of ferric oxide with 
water, and ordinarily presents the composition 2Fe^O"-J-3H^O. 

This hydroxide occurs native as hrown hematite. Another 
mineral, known 2iB goetldte^ contains Fe^O^+H^O. 

Ammonia or potassium hydroxide will at once produce a 
voluminous and flocculent, rust-colored precipitate in a solu- 
tion of ferric chloride. This precipitate constitutes a ferric 
hydroxide. 

But if an excess of tartaric acid be added to the solution of 
a ferric salt, the liquid may be saturated with potassium hy- 
droxide and will still remain clear, no precipitate of ferric 
hydroxide being formed. 

Advantage is taken of this property in analysis for the sepa- 
ration of ferric oxide from other oxides which tartaric acid does 
not retain in solution in an alkaline liquid. 

If a solution of ferric acetate be poured into a dialyser 
(page 209), and the water in the exterior vessel be frequently 
changed, the salt will finally be entirely decomposed. Acetic 
acid will pass through the membrane, while ferric hydrate will 
remain dissolved in the water in the dialyser (Grraham). 

Ferroso-ferric Oxide, Fe^O*. — This compound, also called 
magnetic oxide of iron, occurs native as magnetite, and con- 
stitutes the black scales which form on the surface of iron 
when it is heated to redness in the air ; it may be regarded 
ag a compound of ferrous and ferric oxides. 

FeO + Fe^O^ = Fe^O* 
34 



398 ELEMENTS OF MODERN CHEMISTRY. 



SULPHIDES OF IRON. 

Several sulphides of iron are known. 

The disulphide, or pyrites, FeS^, a largely-diffused mineral, 
is the most important of these sulphides. It occurs in two 
distinct forms : 

Pyrite, which crystallizes in brilliant cubes, or pentag- 
onal dodecahedra, having a yellow color and a metallic 
lustre. 

Marcasite, which forms rhombic prisms, variously modi- 
fied, and presents a dull, greenish-yellow color. This variety 
is much more alterable than the other, and possesses a great 
tendency to attract oxygen from the air and become converted 
into sulphate. When heated in closed vessels, pyrites loses a 
part of its sulphur. 

A combination of monosulphide and sesquisulphide of iron 
is encountered in nature ; it crystallizes in regular hexagonal 
prisms and is called magnetic pyrites. 

Monosulphide of Iron, FeS, is found in small quantity in 
many meteorites. It is ordinarily obtained by heating to red- 
ness in a covered crucible a mixture of three parts of iron- 
filings and two parts of sulphur. When the mixture has 
fused, it is poured out and solidifies to a brittle, blackish mass, 
having a metallic reflection. In this state, it is used for the 
preparation of hydrogen sulphide. 

CHLORIDES OF IRON. 

Ferrous Chloride, FeCP, is obtained anhydrous by the action 
of dry hydrochloric acid gas upon metallic iron. It forms white 
pearly scales. When iron is treated with aqueous hydrochloric 
acid, it dissolves, and hydrogen is disengaged. The green, 
filtered liquid deposits, when sufficiently concentrated, bluish- 
green, oblique rhombic prisms. This is hydrated ferrous chlo- 
ride, FeCP + 4H^0. 

Ferric Chloride, FeCP, is formed when a current of chlo. 
rine is passed over iron-turnings heated in a glass or porcelaiii 
tube. The two bodies combine with incandescence, and if 
the chlorine be in excess, ferric chloride will be obtained as a 
brilliant black, crystalline sublimate. The vapor density of 
ferric chloride above 700° corresponds to FeCP, but at lower 
temperatures its composition is probably Fe'^CP. 



FERROUS SULPHATE. 399 

This body is very soluble in water and forms a yellow-brown 
solution. The latter may be obtained by dissolving ferric oxide, 
such as powdered hematite, in hot hydrochloric acid, or by 
passing chlorine into a solution of ferrous chloride. Ferric 
<jhloride is also soluble in alcohol, ether, and benzene. 

FERROUS SULPHATE. 

FeSO* + 7H20 

This salt has long been known under the names green 
vitriol and copperas. It is obtained by exposing iron pyrites 
to the air, or roasting that mineral at a moderate heat. It is 
generally prepared by dissolving iron in dilute sulphuric acid, 
and it is a residue from the preparation of hydrogen sulphide 
by means of iron sulphide and dilute sulphuric acid. 

It crystallizes in oblique rhombic prisms, containing 7 mol- 
ecules of water of crystallization. When exposed to the air, 
these crystals effloresce slightly, and at the same time their 
surface becomes yellow from absorption of oxygen and the 
formation of ferric subsulphate. 

2FeS0* + = Fe^OCSO*)^^ = Fe^0l2S0^ 

When heated, they lose their water, of which six molecules 
are disengaged at 114°, and the seventh only at 300°. At a 
higher temperature the salt decomposes into sulphurous oxide, 
and a ferric subsulphate different from the preceding. 
2FeS0* = SO^ + (Fe'O')SO' 

The crystals of ferrous sulphate are freely soluble in water. 
100 parts of the salt dissolve in 161: parts of water at 10°, and 
in 30 parts of boiling water. The green solution absorbs oxy- 
gen from the air, becomes troubled, and deposits yellow ferric 
subsulphate. 

Other hydrates of ferrous sulphate are known. According 
to Mitscherlich, a saturated boiling solution of the salt deposits 
at 80° crystals containing four molecules of water. According 
to Marignac, when a solution of ferrous sulphate containing 
free sulphuric acid is evaporated in a vacuum, crystals are first 
deposited which contain 7 molecules of water, then a sulphate 
FeSO* + 5ff 0, and finally, FeSO* -j- IH^O. 

The sulphate FeSO* -f 5H'^0, is isomorphous with crystal- 
lized cupric sulphate (blue vitriol), and like it crystallizes in 
triclinic prisms. 



400 ELEMENTS OF MODERN CHEMISTRY. 

FERRIC SULPHATE. 

re2(S04)3 

This salt is obtained by heating ferrous sulphate with nitric 
and sulphuric acids; the brown solution is evaporated, and the 
residue well dried. 

2FeS0* + H^SO* + = H^O + ¥e\mj 

Ferric sulphate is a slightly-yellowish, white mass, which 
dissolves completely, but very slowly, in water. The solution 
is yellow-brown, and has an acid reaction. 

When concentrated by evaporation, it deposits a deliquescent, 
yellowish, crystalline mass, which constitutes hydrated ferric 
sulphate. 

There are several ferric suhsulphates ; those which have 
been mentioned above result from the action of one molecule 
of ferric oxide upon one or two molecules of sulphuric acid, 
the neutral sulphate resulting from the action of one molecule 
of ferric oxide upon three molecules of sulphuric acid. 

n^SO* + Fe^O^ = WO + (Fe20^)"S0* 

Ferric monosulphate. 

g|g; + Fe'O' = 2H^0 + (Fe^O)" { I^I 

Ferric disulphate. 

ff SO* r so* 

H^SO* + Fe^O^ ==: SH^O + (Fe^)-' \ SO* 

ffso* (.so* 

Ferric trisulphate (normal sulphate), 

FERROUS CARBONATE. 

FeC03 

Spathic iron ore^ which crystallizes in rhombohedra, is fer- 
rous carbonate. When a solution of sodium carbonate is added 
to a solution of ferrous sulphate, a greenish-white precipitate 
is obtained, which rapidly becomes colored in the air, absorb- 
ing oxygen and losing carbonic acid. When recently precipi- 
tated, it dissolves in a large excess of carbonic acid. 

Characters of Ferrous Salts. — The solutions of these salts 
are green ; they are not precipitated by hydrogen sulphide, but 
ammonium sulphide forms a black precipitate of ferrous sul- 
phide. Potassium hydroxide or ammonia produces a greenish- 
white precipitate of ferrous hydroxide, insoluble in an excess of 



COBALT. 401 

tte reagent, and rapidly becoming colored in the air. Potas- 
sium ferrocyanide (yellow prussiate of potash) forms with fer- 
rous salts a light-blue precipitate. Potassium ferricyanide (red 
prussiate) forms a dark-blue precipitate. Solution of gall-nuts 
does not color ferrous salts. 

Characters of Ferric Salts. — Hydrogen sulphide produces 
a precipitate of sulphur, reducing the salts to the ferrous state. 
Ammonium sulphide precipitates them black. Potassium hy- 
droxide and ammonia form red-brown precipitates of ferric hy- 
droxide, insoluble in an excess of the reagent. Potassium ferro- 
cyanide forms a dark-blue precipitate which is Prussian hlue. 

Potassium ferricyanide produces a dark-brown color without 
precipitation. Potassium sulphocyanate gives a blood-red color. 

Solution of gall-nuts forms a bluish-black precipitate which 
constitutes ink. 

COBALT. 

Co =58.55 

Cobalt was discovered by Brandt in 1735. It is found as 
smaltite in the arsenide, CoAs^, and as cobalt glance in the 
sulph-arsenide, CoAsS. Its ores are worked principally for the 
production of a dark-blue, vitreous mass, a combination of cobalt 
silicate and potassium silicate, known as smalt or azure hlue. 

The metal is prepared in the laboratory by calcining its oxa- 
late in a covered crucible. 

CoC^O* = Co + 2C0^ 

Cobalt oxalate. Carbon dioxide. 

It may be obtained as a metallic button by heating the pul- 
verulent metal in a lime crucible in a wind-furnace. The lime 
crucible is placed in another crucible of refractory clay, and 
the space between the two is filled up with fragments of quick- 
lime (H. Sainte-Claire Deville). 

Pure cobalt is silvery-white. It is very malleable ; its den- 
sity is 8.6, and it is magnetic. At ordinary temperatures it is 
unaffected by the air, but at a red heat it is converted into oxide. 

Oxides of Cobalt. — The most important of these are the 
monoxide, CoO, the sesquioxide, Co^O^, and the intermediate 
cobaltoso-cobaltic oxide, Co^O*. 

Cobalt monoxide is obtained as a greenish-gray powder by 
heating the carbonate or hydroxide out of contact with the 
air. It is reducible by hydrogen, carbon, and carbon monoxide. 
aa 34* 



402 ELEMENTS OF MODERN CHEMISTRY. 

Before the blow-pipe it dissolves in fused borax, imparting 
a deep-blue color to the latter. It is used for giving a blue 
color to glass and porcelain. 

^he hydroxide^ Co(OH)^, is obtained by adding an excess 
of potassium hydroxide to the solution of a cobalt salt, and 
boiling the mixture. Its color is pink. 

Cobalt sesquioxide, Co^O^, results when anhydrous cobalt 
nitrate is very gently heated. Its hydroxide, Co(OH)^, is 
obtained as a dark-brown precipitate when the pink-colored 
hydroxide is treated with bromine and caustic potash. 

All these oxides and hydroxides are converted into the 
black cohalfoso-cohaltic oxide, Co^O*, when strongly ignited in 
the air. 

Cobalt Chloride, CoCP. — When pulverulent cobalt is heated 
in a current of chlorine, it takes fire and is converted into a 
chloride, which sublimes in blue scales. A solution of this 
chloride may be obtained by dissolving either monoxide or car- 
bonate of cobalt in hydrochloric acid. The neutral solution is 
currant-red, and on evaporation deposits hydrated crystals of 
the same color. But when it is concentrated, after having 
added hydrochloric or sulphuric acid, it becomes blue. This 
change of color, due to the formation of anhydrous chloride 
even in the midst of the hot liquid, has caused the employ- 
ment of cobalt chloride as a sympathetic ink. Characters 
traced with the dilute solution, which is rose-colored, are invisi- 
ble on white paper, and appear blue only when the paper is 
warmed, again becoming invisible on cooling, by the absorption 
of atmospheric moisture. 

Cobalt Sulphate, CoSO* + 'TH^O.— This salt is found in 
nature, crystallized in oblique rhombic prisms. It may be ob- 
tained by dissolving the oxide or carbonate in dilute sulphuric 
acid and concentrating the red solution. At ordinary temper- 
atures, the latter deposits red crystals, isomorphous with ferrous 
sulphate. Between 40° and 50°, it yields monoclinic crystals, 
containing 6 molecules of water, and isomorphous with mag- 
nesium sulphate of analogous composition. 

Characters of Cobalt Salts.— The cobaltous salts are the 
more important. Their solutions are rose or currant-red, but 
when concentrated and hot they become blue, especially when 
an excess of acid is present. Hydrogen sulphide does not pre- 
cipitate solutions of cobalt salts. Ammonium sulphide forms a 
black precipitate. Potassium hydroxide gives a blue precipitate 



NICKEL. 403 

of a basic salt, which, in presence of an excess of potash, is 
converted into hydroxide of cobalt, having a dirty rose color. 

Ammonia forms a blue precipitate, soluble in excess. 

When heated with borax in the blow-pipe flame, the salts 
of cobalt yield beads of a pure blue color. 



NICKEL. 

Ni = 58.25 

This metal was discovered by Cronstedt in 1731. 

Natural State and Extraction. — Nickel is a constituent 
of many minerals. It occurs as kupfernickel or niccolite, NiAs, 
as nickel glance, NiAsS, as millerite, NiS, and in silicates such 
as the garnierite of New Caledonia. It is also a common 
constituent of cobalt ores, and of magnetic pyrites. Nickel- 
iferous pyrites are mined in enormous quantities at Sudbury, 
in Canada. The commercial extraction of nickel is effected 
by various processes, more or less complicated, according to 
the nature of the ore. The silicate yields a product which is 
free from cobalt. The oxides are readily reducible by carbon. 
Perfectly pure nickel is best obtained electrolytically. 

Properties. — Pure nickel is grayish-white with a yellowish 
tinge. It is malleable, ductile, and very tenacious. Its den- 
sity is 8.279, and may be increased to 8.666 by hammering. 
It is less fusible than iron and more fusible than manganese. 
It is magnetic at ordinary temperatures, but loses this property 
at about 250°. It is unaltered by the air at ordinary tempera- 
tures, but absorbs oxygen at a red heat. It dissolves slowly 
in dilute sulphuric and hydrochloric acids, rapidly in nitric 
acid. In contact with concentrated nitric acid it becomes 
passive like iron. Finely divided nickel combines with carbon 
monoxide at 100°, forming nickel carbonyl, Ni(CO)* (p. 219). 

Nickel is used in various alloys. German silver contains 
50 per cent, copper, 25 nickel, and 25 zinc. The five-cent 
coins of the United States contain 25 per cent, nickel and 
75 copper. An alloy of nickel with steel is at present ex- 
tensively used for armor plates. 

Pure nickel is deposited as a brilliant metallic layer by the 
electrolysis of a solution of nickel and ammonium double sul- 
phate, and this solution is used in nickel-plating. 

Nickel Oxides. — ^A monoxide, NiO, and a sesquioxide, 
Ni^O^, are known. The monoxide is an ash-gray powder, 



404 ELEMENTS OF MODERN CHEMISTRY. 

obtained by strongly calcining the nitrate or carbonate. On 
adding potassium hydroxide to a nickel salt, an apple-green 
precipitate of nickel hydroxide^ Ni(OH)^, is formed. 

Nickel sesquioxide may be obtained by moderately calcining 
the nitrate. It is black. When chlorine gas is passed into 
water holding nickel hydroxide in suspension, a dark-brown pow- 
der is obtained which is a hydrate of the sesquioxide. This 
hydroxide may also be made by precipitating a nickel salt with 
potassium hydroxide mixed with an alkaline hypochlorite. 

When strongly calcined, nickel sesquioxide abandons part of 
its oxygen and is changed into monoxide. Treated with hydro- 
chloric acid, it yields nickel chloride, and chlorine is disengaged. 

Ni^O^ + 6HC1 = 2NiCP 4- 3H^0 -f CP 

Nickel Chloride, NiCP. — This salt may be obtained anhy- 
drous by the action of chlorine on nickel-filings ; it is volatile 
at a dull-red heat, and sublimes in golden-yellow scales. The 
hydrated chloride is formed by the action of boiling water on 
the anhydrous salt, or by the action of hydrochloric acid on the 
oxide or carbonate. Its solution is green, and after proper 
concentration deposits beautiful green crystals which contain 
NiCP + GH^O. 

Nickel Sulphate, NiSO* + YH'O.— The sulphate is depos- 
ited in fine, emerald-green, orthorhombic prisms, isomorphous 
with magnesium sulphate, when its solution is allowed to evap- 
orate spontaneously below 15°. There is another hydrate con- 
taining 6H^0, which is dimorphous. When deposited between 
20 and 30°, it crystallizes in square octahedra, but when its 
solution is made to crystallize between 60 and 70°, monoclinic 
crystals are obtained, isomorphous with the corresponding 
sulphates of magnesium, zinc, and cobalt. 

Nickel sulphate dissolves in 3 times its weight of water at 10°. 

Characters of Nickel Salts. — The nickel salts when hy- 
drated or in solution have a fine emerald-green color. When 
anhydrous they are yellow. 

Hydrogen sulphide does not precipitate them from acid solu- 
tions. Ammonium sulphide throws down a black precipitate. 
Potassium hydroxide and potassium carbonate form apple- 
green precipitates. 

In neutral solutions, ammonia gives a green precipitate of 
nickel hydroxide, which dissolves in an excess of ammonia, 
forming a blue solutidn. 



MANGANESE. 405 

MANGANESE. 

Mn =. 54.8 

This metal may be obtained from the chloride by electro- 
lysis, or by reduction with sodium. It is more conveniently 
prepared by reducing its oxides with aluminium or carbon 
at high temperatures. The reduction with carbon is best 
effected in the electric furnace, and an excess of this ele- 
ment should be carefully avoided on account of the remark- 
able tendency of manganese to form a carbide. 

The properties of manganese are greatly modified by the 
presence even of small amounts of impurities. The pure 
metal is described as rather soft and malleable, while the 
commercial product is very hard and brittle. The color of 
manganese is grayish white. Its density is about 7.4, and 
it melts only at a high white heat. It is unaffected by air 
or moisture at ordinary temperatures, but decomposes water 
and is superficially oxidized at 100°. It dissolves readily in 
dilute mineral acids. 

Manganese enters into the important alloys ferromanganese 
and spiegeleisen, which are made directly in the blast furnace. 
Manganese bronze contains about 10 per cent, manganese and 
90 per cent, copper. 

MANGANESE OXIDES. 
Manganese forms six compounds with oxygen : 

Manganous oxide MuO 

Manganoso-manganic oxide Mn^^O* 

Manganic oxide ' Mn^O^ 

Manganese dioxide [ MnO^ 

Manganic anhydride . . MnO^ 

Permanganic anhydride '. Mn^O'^ 

Manganous oxide is formed when manganous carbonate is 
strongly heated in a current of hydrogen, or by reducing one 
of the higher oxides in a current of hydrogen or carbon mon- 
oxide. It is a grayish-green powder which slowly absorbs 
oxygen at ordinary temperatures, and takes fire at a tempera- 
ture below redness, forming the red oxide, Mn'^O*. 

^ The latter body is also formed by the calcination of the 
dioxide. It is analogous to the magnetic oxide of iron, and 
constitutes the mineral known as hausmannite. 

Manganic oxide^ Mn^O^ occurs in nature in tetragonal 
pyramids as hraunite. 



406 ELEMENTS OF MODERN CHEMISTRY. 

MANGANESE DIOXIDE. 

(BINOXIDE OR PEROXIDE OF MANGANESE.) 



MnO 



This important body is found abundantly in nature ; it con- 
stitutes the mineral pyrolusite. It may be obtained pure and 
anhydrous by exposing a concentrated solution of manganous 
nitrate to heat and gradually raising the temperature to 155°. 
Nitrous vapors are evolved, and a brilliant brown-black mass is 
obtained, which is the dioxide. 

Mn(NO^y = MnO^ + mO'' 

It loses one-third of its oxygen when heated to redness, and 
is converted into the red oxide. When heated with concen- 
trated sulphuric acid, it loses half of its oxygen, manganous 
sulphate being formed. 

MnO^ H- H^SO* -= MnSO* + H^O + 

With hydrochloric acid it yields water, chlorine, and manga- 
nous chloride. 

A hydrate of manganese dioxide is formed when an excess 
of chlorine is directed into water holding in suspension man- 
ganous hydrate or carbonate. This hydrate is a dark-brown 
powder. 

Manganese dioxide is largely employed for the preparation 
of oxygen and chlorine. It is used to decolorize glass black- 
ened by carbonaceous matters or rendered green by a trace of 
iron. 

MANGANIC ACID. 

When manganese dioxide is heated with potassium hydrate 
in a silver crucible, and the calcined mass is exhausted with 
water, the latter dissolves out potassium manganate. A dark- 
green liquor is thus obtained which, when evaporated in vacuo, 
deposits a crystalline mass. These crystals may be drained on 
a porous porcelain plate, and green needles of potassium man- 
ganate, K^MnO^, remain. The salt is isomorphous with the 
sulphate K^SO*. 

When the green solution is boiled, it becomes red and deposits 
brown flakes of hydrated manganese dioxide : the red liquor is 
a solution of potassium permanganate, this salt beins formed at 



PERMANGANIC ACID — MANGANOUS SULPHATE. 407 

the expense of the manganate, which breaks up into hydrated 
dioxide, potassium hydroxide, and permanganate. 

SK^MnO* H- 3H^0 =- 2KMnO* + MnOlH^O + 4K0H 

Potassium Potassium Hydrated manganese 

manganate. permanganate. dioxide. 

An analogous decomposition takes place when an acid is 
added to the green solution of manganate ; a manganous salt 
and permanganic acid are formed, and the latter colors the 
liquid red. 

PERMANaANIC ACID. 

Potassium permanganate, KMnO*, is an important salt. It 
is prepared by heating to dull redness a mixture of manga- 
nese dioxide, potassium hydroxide, and potassium chlorate. 
After cooling, the product is exhausted with boiling water, 
and when the liquid has assumed a purple color, it is de- 
canted, and, after neutralization by nitric acid, is evaporated 
at a gentle heat. On cooling, it deposits crystals that may 
be dried on a porous tile. 

Potassium permanganate crystallizes in almost black needles, 
having a metallic reflection. It dissolves in 15 or 16 parts of 
cold water, and its solution has a magnificent, intense purple 
color. 

If solution of sulphurous acid be added to potassium per- 
manganate solution, the latter is instantly decolorized, and the 
liquid contains only potassium sulphate and manganese sulphate. 

If a drop of the solution of potassium permanganate be 
placed upon a sheet of paper, it loses its color and a brown 
stain of hydrated manganese dioxide is produced. 

These experiments indicate the oxidizing properties of the 
permanganate. In the first, sulphurous acid was oxidized ; in 
the second, it was paper, of which the carbon and hydrogen 
removed the oxygen from the permanganate, which was thus 
reduced to dioxide. 

MANOANOUS SULPHATE. 

MnSO* + 7H20 

This salt may be prepared by dissolving manganous carbon- 
ate in sulphuric acid. The properly concentrated rose-colored 
solution deposits, between and 6°, oblique rhombic prisms, 
isomorphous with green vitriol and containing 7 molecules of 
water. 



408 ELEMENTS OF MODERN CHEMISTRY. 

Between 7 and 20°, manganous sulphate crystallizes with 5 
molecules of water, like cupric sulphate, with which it is then 
isomorphous. 

Between 20 and 30°, it is deposited in oblique rhombic 
prisms, according to Marignac, which contain only 4 molecules 
of water. 

All of these crystals are pink-colored, and their color is 
deeper as they contain more water of crystallization. They are 
very soluble in water. 

MANGANOUS CAEBONATE. 

MnC03 

The residues from the preparation of chlorine may be used 
for making this salt. They are evaporated, without filtering, 
in a porcelain capsule, with frequent stirring, and the dry 
residue is calcined with an excess of manganese dioxide. The 
ferric chloride which was mixed with the manganous chloride 
is decomposed or volatilized during this operation. Ferric 
oxide remains, mixed with the excess of manganese dioxide 
and the manganous chloride, which resists the heat. The latter 
is extracted by exhausting the mass with boiling water. A 
rose-colored solution is thus obtained which often contains a 
small quantity of cobalt chloride. The latter is precipitated 
as sulphide by adding little by little a solution of sodium sul- 
phide. As soon as the precipitate, which is at first blackish, 
begins to assume a flesh tint, the liquid is filtered and precipi- 
tated by sodium carbonate. 

Manganese carbonate constitutes a white powder with a paW 
rose tint. When heated in contact with air, it gives up car- 
bonic acid gas and is converted into red oxide of manganese. 

Characters of Manganese Salts. — The salts of manganese 
are colorless or have a light pink color. Their solutions are 
not precipitated by hydrogen sulphide. Ammonium sulphide 
gives a flesh-colored precipitate ; sodium carbonate, a dirty 
white. Potassium hydroxide produces a dirty white precipitate 
of manganous hydroxide, which rapidly becomes brown by ab- 
sorbing oxygen from the air. 

When heated in the blow-pipe flame with a small quantity 
of potassium hydroxide or nitrate, the salts of manganese give 
a bead which dissolves in water with a green color (manganate). 



URANIUM. 409 

URANIUM. 

U = 237.8 

Uranium is related to manganese and iron by certain com- 
pounds, and there are others which relate it to chromium, molyb- 
denum, and tungsten. The latter three elements combine with 
oxygen, forming the anhydrides of energetic acids, and their 
atoms may be regarded as hexatomic. 

Uranium is not found in abundance, although it is widely 
distributed. It occurs in pitchblende, a uranoso-uranic oxide, 
uranite, a calcium uranyl-phosphate, and in other minerals, 
associated with copper, bismuth, arsenic, etc. Euxenite con- 
tains niobate and titanate of uranium. 

The metal may be prepared by the action of sodium on a 
mixture of uranium chloride, UCl*, and potassium chloride, the 
latter being employed as a flux. Mo^ssan has recently pre- 
pared considerable quantities of uranium by reducing the 
oxides with carbon in the electric furnace. 

So obtained, uranium is of an iron or nickel color, not quite 
as hard as steel, and has a density of 18.4. When heated in 
the air, it is oxidized with incandescence. It does not decom- 
pose water, but dissolves in dilute acids, disengaging hydrogen. 

Uranium Oxides. — The principal oxides are IJO^ and 
UO^, besides which there exist several intermediate oxides, 
and probably a uranic oxide, UO*. 

Uranmm Dioxide, UO^, was at first believed to be the free 
metal. It is a brown powder, and may be obtained by strongly 
heating uranic oxide with charcoal or in a current of hydro- 
gen. Prepared in the latter manner, the monoxide is pyro- 
phoric. A corresponding hydroxide is formed when solutions 
of uranous salts are precipitated by alkaline hydroxides. 

Uranic Oxide, UO^, is obtained as a light-brown powder by 
heating uranyl nitrate to 250°. When heated to redness, it is 
converted into green uranoso-uranic oxide WO^. Uranic oxide 
combines with bases forming a series of salts of the general 
formula R^U^O^ in which R is one atom of a monatomic metal. 
The uranates are yellow, insoluble in water, but soluble in acids. 
The alkaline uranates may be obtained by precipitating a uranyl 
salt (see farther on) with an excess of alkaline hydroxide. 

Sodium Uranate, Na^U^O'', is known in commerce as uranium 

yellow, and is used for painting on porcelain, and for coloring 

a yellow glass which is highly fluorescent. It is prepared in the 

arts by heating in a reverb eratory furnace a mixture of lime 

s 35 



410 ELEMENTS OP MODERN CHEMISTRY. 

and pitchblende. The calcium uranate so formed is decom- 
posed by sulphuric acid, and the uranyl sulphate obtained is 
treated with sodium carbonate. On adding very dilute sul- 
phuric acid, uranium yellow is precipitated. 

Uranium Chlorides. — There are three chlorides, UCP, 
UCl^ UCP, and an oxychloride, UO'CP. The tetrachloride is 
formed by the action of chlorine on a heated mixture of char- 
coal and any oxide of uranium. It is a very deliquescent body, 
crystallizing in lustrous black or dark -green regular octahedra. 

Salts of Uranium. — These include the uranous salts, and 
those formed by the diatomic radical uranyl^ UO^. The former 
salts are green, and are converted by oxidizing agents into 
the corresponding uranyl salts which are yellow. 

Uranyl nitrate^ UO^(NO^)^, which may serve as a starting- 
point for the preparation of uranium compounds, may be 
made from pitchblende. The latter is pulverized, roasted, and 
treated with nitric acid. The solution is evaporated to dry- 
ness, the residue exhausted with water, and the liquid filtered. 
The yellowish-green filtrate is concentrated, and the confused 
crystalline mass which separates on cooling is drained and 
recrystallized, first, from hot water, then from ether, which 
dissolves only the uranyl nitrate, leaving the impurities. 
Uranyl nitrate forms large, yellow, orthorhombic prisms. 

Helium, He = 4. — When certain pitchblendes, notably 
cleveite, are treated with dilute acids, a colorless gas is given 
off (Hillebrand). Ramsay has shown that this gas, which 
was believed to be pure nitrogen, contains another element, 
to which he gave the name of helium, because he regards it 
to be identical with the hypothetical helium to which certain 
lines in the solar spectrum are ascribed. It appears probable 
that helium is a mixture of at least two new elements. Its 
density is 2, and its molecules consist of single atoms. Of 
all known gases, it has the smallest solubility in water and the 
lowest critical temperature. Dewar has succeeded in lique- 
fying it. Like argon, helium is devoid of chemical afl&nity. 



CHKOMIUM. 

Cr = 51.7 

Chromium was discovered in 1797, by Vauquelin, in a 
mineral from Siberia known as crocoite, and which is chro- 
mate of lead. It forms one of the elements of chrome iron 



COMPOUNDS OF CHROMIUM AND OXYGEN. 411 

ore, a combination of cliromium oxide witli ferrous oxide, 
Cr^O^FeO, wliicli corresponds to magnetic oxide of iron, 
Fe^OlFeO. 

Cliromium has only recently been obtained in the reguline 
state and in notable quantity by Moissan, He reduced the 
sesquioxide with carbon in the electrical furnace, thus obtain- 
ing a metal rich in carbon. The latter was eliminated as 
calcium carbide by fusing the mass successively with lime 
and with calcium chromium oxide. So prepared, chromium 
is a brilliant metal, its polished surface being whiter than 
iron. Its density is 6.92. It is infusible except in the elec- 
trical furnace. It is not very hard, though the carbides C^Cr^ 
and CCr*, are exceedingly hard, and it is entirely non-mag- 
netic. At high temperatures it combines energetically with 
oxygen and with sulphur. It also forms definite compounds 
with carbon, silicon, and boron. Hydrochloric and sulphuric 
acids dissolve it, especially by the aid of heat while it is unaf- 
fected by strong nitric acid. 

Chromium has also been obtained by electrolysis of its 
chloride, as well as by reduction of its oxide by metals like 
aluminium and magnesium. 

COMPOUNDS .OF CHROMIUM AND OXYGEN. 

There are two well-defined compounds of chromium and 
oxygen, the green oxide, Cr^O^ and chromic anhydride, CrO^. 

Chromium Oxide, Cr^O^ is a green powder; it may be 
obtained by calcining mercurous chromate. 

2Hg-^CrO* = 4Hg + 0^ + Cr^O' 

Another process consists in heating in a crucible a mixture 
of 2 parts of potassium dichromate with a little more than 1 
part of flowers of sulphur. After cooling, the mass is treated 
with water, which dissolves out potassium sulphate and leaves 
chromium oxide. 

Chromium oxide is undecomposable by heat, and melts only 
at the temperature of the forge. It forms several different 
hydrates. When ammonia is added to the green solution of 
chromic chloride, a green, flaky precipitate of chromic hydrox- 
ide is formed; it is soluble in acids and in potassium hydroxide. 

Chromic Anhydride, CrO^ is prepared by gradually adding 
to a cold saturated solution of potassium dichromate IJ times 



412 ELEMENTS OP MODERN CHEMISTRY. 

its volume of sulplmric acid. The chromic anhydride, ordi- 
narily called chromic acid, set free separates in needle-shaped 
crystals of a dark-red color, which should be drained and 
recrystalized in a small quantity of warm water. 

It is deliquescent ; its aqueous solution has a dark yellow- 
brown color. It is an energetic oxidizing agent. Hydrochlo- 
ric acid converts it into chromic chloride, with evolution of 
chlorine. 

2CrO^ -\- 12HC1 =2CrCP+ 6H^0 + 3CP 

If a concentrated solution of sulphurous acid be added to a 
solution of chromic acid, the liquid immediately becomes green 
from the formation of chromic sulphate. 

Chromates. — The most important chromates are those of 
potassium and lead. 

Potassium neutral chromate, K^CrO*, crystallizes in lemon- 
yellow, right rhombic prisms, isomorphous with potassium sul- 
phate. It is very soluble in water, to which it communicates 
an intense yellow color. So great is its coloring property, that 
one part of chromate will sensibly color 40,000 parts of water. 

Potassium dichromate^ K^Cr^O^ is prepared from chrome 
iron ore. The finely-powdered mineral is intimately mixed 
with potash and nitre, and the mixture fused at a red heat. 
After cooling the mass is exhausted with water, which dissolves 
the neutral chromate. The requisite quantity of sulphuric or 
acetic acid is then added to convert this into the dichromate, 
and, after allowing it to settle (to remove silica, etc.), the red 
solution is evaporated to crystallization. 

Potassium dichromate is a beautiful salt of an orange-red 
color. It crystallizes in quadrangular tables or prisms be- 
longing to the triclinic system. 

It dissolves in 8 or 10 parts of cold water and in a much 
less quantity of boiling water. 

A strong heat decomposes it into neutral chromate, chromium 
oxide, and oxygen. 

4K^Cr^0'^ = 4K2CrO* + 2Cr^0^ -f- 30^ 

When heated with sulphuric acid, it loses oxygen and is 
converted into chromic sulphate and potassium sulphate. 

2K2Cr20^ + 8ffS0* = 2Cr=^(S0*)' + 2X^80* + 8H^0 + 30^ 



COMPOUNDS OF CHROMIUM AND CHLORINE. 413 

The residue when exhausted with water yields a green 
solution, which deposits on evaporation beautiful octahedral 
crystals of a violet-black color, constituting chrome alum. 

CrXS0^)lK2S0^ + 24ffO 

Sulphurous acid reduces potassium dichromate in the cold, 
also yielding chrome alum if sulphuric acid be added. 

K^Cr^O^ -I- 3S0^ + H^SO^ = CrXSOO'.K^SO* -f H^O 

The constitution of potassium dichromate is represented by 
the formula 

KOCrO^ 

> 

KOCrO^ 

COMPOUNDS OF CHROMIUM AND CHLORINE. 

Several combinations of chromium and chlorine are known. 
The most important is the violet chloride, CrCP, correspond- 
ing to aluminium chloride and ferric chloride. It is prepared 
by passing chlorine gas over an intimate and perfectly dry 
mixture of chromium oxide and charcoal, heated to redness in 
a porcelain tube ; carbon monoxide is disengaged, and chromic 
chloride sublimes into the cooler portion of the tube in brilliant 
peach-blossom-colored scales. 

These crystals are almost insoluble in cold water, and dis- 
solve but slowly in boiling water. Hydrogen reduces them at a 
red heat, with formation of hydrochloric acid, and a chloride, 
CrCP, which crystallizes in white scales (Peligot). 

2CrCP -f H^ = 2HC1 -f- 2CrCP 

If a small quantity of the chloride CrCP, be added to hot 
water, holding in suspension the violet chloride CrCP, the 
latter will be instantly dissolved, forming a green solution. 

Chromyl chloride, CrO^CP, is obtained by heating a pre- 
viously fused mixture of common salt and potassium di- 
chromate with sulphuric acid ; abundant red vapors are disen- 
gaged, and condense to a blood-red liquid. This body boils 
at 116.8°. Its density at 25° is 1.920 (Thorpe). On contact 
with water it decomposes into hydrochloric acid and chromic 
anhydride. 

CrO^CP -f WO = CrO' + 2HC1 
35^ 



414 ELEMENTS OF MODERN CHEMISTRY. 



MOLYBDENUM. 

Mo = 96 

This metal is prepared by reducing molybdic oxide, MoO', 
by a current of hydrogen at a high temperature. It is a white, 
very hard, and almost infusible metal, having a density of 9.01. 
It forms five oxides, MoO, Mo^O^ MoO^ Mo^O^ and MoO^ 
and the chlorides MoCP, MoCP, MoCl*, and MoCP. 

Molybdic Oxide, MoO^ is obtained by roasting the native 
sulphide, molybdenite, MoS^, which occurs in black foliated 
masses closely resembling graphite, and capable of marking 
paper in the same manner. The roasting is conducted at a 
temperature not above redness, and the resulting oxide is dis- 
solved in ammonia, and the solution filtered. On evaporation 
and cooling, crystals of ammonium molybdate are obtained 
which yield molybdic oxide when calcined in the air. 

Molybdic oxide is a white, fusible, and volatile powder ; it 
is but slightly soluble in water ; the solution, however, being 
acid. It is the anhydride of an acid which forms a somewhat 
complicated series of salts, one of the most important being a 
molybdate of ammonium having the composition 

Mo^O^*(NH0'+4H2O = 3(NH*)2MoO*4-4H2MoO^ 
This is the compound which is formed when a solution of mo- 
lybdic oxide in ammonia is evaporated. It is employed in the 
laboratory as a test for phosphorus. When its solution in nitric 
acid is added to a warm solution containing phosphoric acid, a 
yellow precipitate containing molybdic acid, ammonia, and phos- 
phoric acid, is thrown down. This precipitate is insoluble in 
nitric acid, but soluble in ammonia. 



TUNGSTEN. 

W (Wolframium) = 184 

Tungsten occurs in a number of minerals, associated princi- 
pally with tin ores. Wolfram is tungstate of iron and manga- 
nese. Scheelite is calcium tungstate ; stolzite or scheelitine is 
tungstate of lead. 

The metal may be obtained by reducing tungstic oxide, 
WO^, by means of either carbon or hydrogen at very high 
temperatures. It is of a steel-gray color, very hard and brittle. 



TUNGSTEN. 415 

and extremely refractory. Its density is 19.1. It is not tar- 
nished by air under ordinary conditions, but when heated in 
the form of powder it takes fire, forming tungstic oxide. 
Another oxide, WO''', and four different chlorides of tungsten 
— WCP, WCP, WCP, and WCP— are known to exist. 

Tungstic Oxide, WO^ occurs native in a yellow powder 
called wolfram oclire. It may be prepared from scheelite or 
from wolfram. The mineral is treated with nitro-muriatic acid, 
and the undissolved residue, consisting of tungstic oxide, is 
dissolved in ammonia. The filtered solution is evaporated to 
dryness, and on calcination the ammonium tungstate leaves 
tungstic oxide as pale yellow scales. It is fusible at a high 
temperature, insoluble in water and acids, soluble in alkaline 
solutions with formation of tungstates. 

Tungstic oxide is the anhydride of several acids forming 
well-marked salts. 

Normal tungstic acid, H^WO*, is precipitated as an insolu- 
ble yellow powder when the solution of a tungstate is decom- 
posed by an excess of hot acid. 

The alkaline normal tungstates have the general formula 
K^WO"*. Besides these, there are highly complicated salts 
derived from the condensation of several molecules of the 
normal salts. One of these, known as sodium paratungstate, 
is prepared on a large scale by roasting wolfram with sodium 
hydrate and exhausting the mass with water. Its composition 
is Na^°W"0*^ : it is used as a mordant in dyeing, and has been 
recommended for rendering fabrics of vegetable origin non- 
inflammable. The goods are treated with a solution containing 
twenty per cent, of sodium tungstate and three per cent, of 
sooium phosphate. 

The remaining elements are tetratomic, some of them at the 
same time forming unsaturated compounds in which the me- 
tallic atom may be diatomic, as in the oxides of tin, Sn'^0^ 
and Sn"0. Or two atoms of the metal may form a hexatomic 
couple, as in titanium sesquioxide, Ti^O^ 

Tin, titanium, zirconium, and thorium form a group of 
which the chemical analogies become evident in a comparison 
of the composition and relations of similar compounds, while 
platinum is the most important member of another group of 
metals which are associated together in nature, and which are 
related by certain chemical and physical properties. 



416 



ELEMENTS OP MODERN CHEMISTRY. 



Tnsr. 

Sn (Stannum) = 118.15 

Natural State and Extraction. — The only mineral of tin 
wliich is worked is the dioxide (cassiterite). It is found in 
veins in the oldest formations, or disseminated in sand produced 
by their disaggregation. The principal tin mines are in India, 
in Malacca and the island of Banca, in Wales and in Saxony. 
Tin ore generally occurs mixed with various other minerals, 
such as sulphide and sulph-arsenide of iron, sulphides of copper 
and tin, etc. It is crushed and washed in order to remove 
light, earthy matters, and then roasted. The sulphides and 
sulph-arsenides are thus oxidized and disintegrated, and the 

product is submitted to a sec- 
ond washing which removes 
the lighter oxides, leaving the 
cassiterite. The latter is then 
heated with charcoal in a 
cupola-furnace, represented in 
Fig. 119 ; it is a sort of pris- 
matic furnace, having a hearth 
at the bottom where the melted 
metal collects. Air is blown 
in through the tuyere D. Car- 
bon monoxide is formed, and 
this reduces the stannic oxide ; 
|| the tin collects on the hearth, 
^j| from which it is drawn into 
^ : the basin I, where it is stirred 
with rods of green wood. The 
steam and gases produced by 
the carbonization of the wood, agitate the melted mass and bring 
to the surface the foreign matter or dross, which is removed. 
The tin is then run into moulds. 

Thus obtained, tin generally contains small quantities of 
copper, iron, lead, antimony, and arsenic. It is purified by 
slowly heating it on the hearth of a reverberatory furnace; 
the pure tin melts first and runs out of the furnace, while the 
less fusible alloys remain upon the hearth. This method of 
purification is called liquation. 

Properties. — Pure tin is a white metal, resembling silver in 




Fig. 119. 



TIN. 417 

its color and lustre. It melts at 228°, and crystallizes when 
slowly cooled. Crystals of tin, belonging to the type of the 
right square prism, may also be obtained by galvanic precipi- 
tation of the metal. Their density is 7.178. That of the 
fused and slowly-cooled metal is 7.373 (H. Deville). 

Tin is ductile and malleable. When a bar of tin is bent, 
it produces a peculiar noise called the cry of tin. 

The metal is unaltered by the air, but when fused, rapidly 
becomes covered with a grayish pellicle of oxide. Tin dis- 
solves in concentrated hydrochloric acid, disengaging hydrogen. 
The action is rapid when heat is applied. 

If ordinary nitric acid be poured upon granulated tin, an 
energetic action takes place immediately. The tin is converted 
into a white powder of dioxide, and torrents of red vapors are 
evolved. 

Very dilute nitric acid attacks tin almost without disengage- 
ment of gas. After some time the liquid will be found to con- 
tain a small quantity of tin nitrate and ammonium nitrate. 
The ammonia is formed by the simultaneous reduction of water 
and nitric acid by the tin. 

HNO^ + H^O = 20^ + NH^ 

When tin is heated with a concentrated solution of either 
potassium or sodium hydroxide, hydrogen is disengaged, and 
an alkaline stannate is formed. 

Uses of Tin. — Tin enters into the composition of bronzes ; 
it is made into dishes and covers, and the thin foil in which 
various substances, such as chocolate and tobacco, are enveloped. 

Tinning of kitchen vessels consists in covering them with a 
thin coating of tin. This protects the copper or iron from the 
action of the acids which enter into the composition of various 
articles of food. The objects to be tinned are first well cleaned 
by rubbing them with sand, and are then dipped into melted 
tin. After separating the excess of metal, they are polished 
by rubbing with cloths dipped in sal ammoniac. 

Tin-plate is sheet-iron covered with a thin layer of tin. The 
iron is first dipped into dilute sulphuric acid to remove the 
oxide; it is then rubbed with sand, and afterwards plunged 
successively into a bath of melted tallow and a bath of tin covered 
with tallow. On contact with the iron, the tin enters into com- 
bination, forming a true alloy, which becomes covered with a 
coating of pure tin. 
ib 



418 ELEMENTS OF MODERN CHEMISTRY. 

When the surface of tin-plate is washed with a mixture of 
hydrochloric and nitric acids, the superficial coat of tin is dis- 
solved, and the crystallized alloy of tin and iron is exposed. 
This is called crystallized tin-plate. 

COMPOUNDS OF TIN AND OXYGEN. 

Tin forms two compounds with oxygen, stannous oxide, SnO, 
and stannic oxide, SnO^. The first is of but little importance. 
It is obtained by precipitating a solution of stannous chloride 
by potassium hydroxide, and boiling the precipitate, by which 
the white, stannous hydroxide first formed loses water and is 
converted into black stannous oxide. When the latter is 
moderately heated in contact with the air, it becomes incan- 
descent and is converted into stannic oxide. 

STANNIC OXIDE. 
Sn02 

This body is found in nature as cassiterite, in the form of 
beautiful, hard, transparent crystals of a yellowish-brown color, 
belonging to the tetragonal system. From this mineral the tin 
of commerce is extracted. 

The white powder obtained when the metal is treated with 
nitric acid is a stannic hydrate, which plays the part of an acid, 
and was named by Fremy metastannic acid. He attributes to 
it the composition 5(H*SnO*). It would be a polymer of 
normal stannic acid. 



^^J 0* = (onysn^' 



When heated to 100°, this hydrate loses half of its water; 
at a red heat, it loses the remainder and is converted into stannic 
oxide. 

When ammonia is added to an aqueous solution of stannic 
chloride, a white, gelatinous precipitate is formed, constituting 
a hydrate. 

This is the stannic acid of Fremy. It dissolves readily in 
hydrochloric acid, and the solution behaves as would an aqueous 
solution of stannic chloride. 

H^SnO^ + 4HC1 = SnCl* + 3H^0 



SULPHIDES OF TIN — STANNOUS CHLORIDE. 419 

It reacts with tlie bases, forming stannates of whicli the 
general composition is expressed by the formula: 



E^SnO^ 



_ Sn ) ^3 
— E^ 1^ 



When heated to 140°, or even when dried for a long time 
in a vacuum, it becomes insoluble in acids. 

SULPHIDES OF TIN. 

Two sulphides of tin are known : a monosulphide, SnS, and 
a disulphide, SnSl The first is obtained by heating tin-filings 
with flowers of sulphur : the product still contains an excess 
of tin, and it is necessary to again heat it with a fresh quantity 
of sulphur. It is a crystalline, lead-colored mass. 

Tin disulphide or stannic sulphide is prepared by first making 
an amalgam of 12 parts of tin and 6 parts of mercury ; this is 
pulverized and the powder is mixed with 7 parts of flowers of 
sulphur and 6 parts of sal-ammoniac. The mixture is intro- 
duced into a matrass of hard glass and gradually heated to 
dull redness on a sand-bath. Sulphur, sal-ammoniac, sulphide 
of mercury, and stannous sulphide are condensed in the upper 
part of the matrass, of which the interior becomes covered with 
a yellow crystalline mass of stannic sulphide. The presence 
of sal-ammoniac and mercury, which volatilize in this opera- 
tion, prevents an elevation of temperature, which would decom- 
pose the stannic sulphide. The latter is carried with their 
vapors, and condenses in brilliant, gold-like scales, which are 
greasy to the touch. This body is known as mosaic gold. It 
is decomposed by a red heat into stannous sulphide and sul- 
phur. It is used for coating the cushions of electric machines, 
to imitate gilding, and very extensively as a pigment; 

STANNOUS CHLORIDE. 
SnCP 

This compound may be prepared anhydrous by heating tin 
in hydrochloric acid gas. Hydrogen is evolved, and a white 
or grayish mass remains, which has a greasy appearance, and 
is almost transparent. It fuses at 250°, and boils at about 
600°. This is stannous chloride. 

When tin is dissolved in hot, concentrated hydrochloric acid 
and the limpid solution is evaporated and allowed to cool, 
beautifal transparent crystals are obtained, which contain 



420 ELEMENTS OF MODERN CHEMISTRY. 

SnCP -f- 2H^0. This is known in commerce as tin salt or tin 
crystals. 

The crystals of stannous chloride dissolve in a small quan- 
tity of water, forming a limpid liquid, but when treated with 
a large quantity of water, they yield a cloudy liquid, which 
holds in suspension a small quantity of white oxychloride. 
The atmospheric oxygen dissolved in the water takes part in 
this decomposition of stannous chloride, from which it removes 
part of the metal, a corresponding quantity of stannic chloride 
(tetrachloride) being formed. 

Stannous chloride reduces many oxygenized and chlorinated 
compounds. It decomposes the salts of silver and mercury, 
setting free the metal. It instantly decolorizes the purple 
solution of potassium permanganate. 

If a solution of stannous chloride be added to a solution of 
corrosive sublimate (mercuric chloride), a white precipitate of 
calomel (mercurous chloride) is instantly formed. By adding 
an excess of stannous chloride, all of the chlorine may be re- 
moved from the mercuric chloride, and a gray precipitate of 
metallic mercury will be formed. 

Stannous chloride is employed as a mordant in dyeing. 



STANNIC CHLORIDE (TETRACHLORIDE OF TIN). 

SnCl* 

If thin tin-foil be thrown into a jar of chlorine gas, the 
metal will take fire, and in presence of an excess of chlorine 
will be converted into anhydrous stannic chloride. This is 
liquid, and gives off white fumes in the air. It was formerly 
known as fuming liquor of Lihavius. 

It is prepared by passing dry chlorine upon tin contained in 
a small retort. The anhydrous chloride condenses in the re- 
ceiver in the form of a yellow liquid. It may be decolorized 
by rectification with a small quantity of mercury, which removes 
the excess of chlorine. 

Tin tetrachloride boils at 120°. Its density is 2.28. A 
small quantity of water added to it is absorbed with a hissing 
noise, and the formation of a crystalline deposit of a hydrate, 
SnCl* + 5H^0. 

These crystals may also be obtained by dissolving tin in aqua 
regia and evaporating the solution, or, again, by passing chlo- 



TITANIUM. 421 

rine into a solution of stannous chloride and concentrating the 
solution. 

The crystals of hydrated stannic chloride dissolve in water, 
forming a clear solution. 

Characters of Stannous Solutions. — Brown precipitates 
are formed by both hydrogen sulphide and ammonium sulphide ; 
the precipitate dissolves in yellow ammonium sulphide. 

Potassium hydroxide forms a white precipitate, soluble in 
an excess of reagent; ammonia yields a white precipitate, in- 
soluble in excess. 

An excess of stannous chloride produces a gray precipitate 
of metallic mercury in a solution of mercuric chloride. 

Chloride of gold gives a purple precipitate (purple of Cas- 
sius) in dilute stannous solutions. 

Characters of Stannic Solutions. — Hydrogen sulphide and 
ammonium sulphide form yellow precipitates, soluble in a large 
excess of the latter reagent. Potassium and sodium hydroxides, 
and ammonia water all form white precipitates, disappearing 
in an excess of the reagent. 

Chloride of gold does not precipitate stannic solutions. 

A sheet of iron or zinc will precipitate the tin from either 
stannous or stannic solutions in gray scales, which assume the 
metallic lustre when burnished. 



TITANIUM. 

Ti = 47.79 

Titanium occurs as the dioxide, TiO^ in rutile, anatase, 
and brooJcite, and with iron in ilmenite (Fe,Ti)'^0^, and in 
many iron ores. Cubical copper-colored crystals of a nitro- 
cyanide of titanium are frequently found in the cinders of 
blast-furnaces in which titaniferous ores are reduced. The 
metal has been obtained by reduction of the oxide by carbon 
in the electric furnace (Moissan). It manifests a remarkable 
affinity for nitrogen. 

Titanium forms three chlorides, TiCP, Ti^CP, and TiCl*; 
there are two well-defined oxides, Ti^O^ and TiO^ and possibly 
a third, TiO. These compounds sufficiently characterize the 
element as a chemical analogue of tin. 

Titanium Dioxide, TiO^ as before mentioned, occurs in 
three different crystalline forms in nature j as square prisms in 

36 



422 ELEMENTS OP MODERN CHEMISTRY. 

rutile, square octahedra in anatase, and orthorhombic prisms 
in brookite. When prepared in a pure form from either of 
these minerals, it is a white, infusible, insoluble powder. Like 
stannic oxide, it is the anhydride of an acid forming a well- 
marked series of titanates. 



GERMANIUM. 

Ge = 72.3 

In 1886, Winkler discovered in a rare silver ore argyrodite^ 
found near Freiberg, a new element corresponding in proper- 
ties with one whose existence had been predicted by Mendele- 
jeff under the name ehasilicon. This metal constitutes about 
7 per cent, of argyrodite, and has also been found in euxenite. 
It may be isolated by the reduction of its oxide by hydrogen 
or carbon, or of potassium-germanium fluoride by hydrogen 
or sodium. 

Germanium crystallizes in brilliant regular octahedra, 
having a density of 5.469, and melting at about 900°. It 
forms two oxides, GeO and GeO^, a sulphide GreS, a chloride 
GeCl*, and probably also a chloride G-eCP. Its properties as 
well as most of those of its compounds agree remarkably 
with the predictions of Mendelejeff. 



ZIRCONIUM. 

Zr = 89.9 

This metal also resembles tin in its chemical relations. Its 
principal mineral is a silicate known as zircon. It may be 
obtained crystallized, amorphous, and in a condition resembling 
graphite. 

Crystallized zirconium may be made by fusing in a carbon 
crucible potassium zirconium double fluoride with aluminium. 
On cooling, the excess of aluminium is dissolved in dilute 
hydrochloric acid, and zirconium remains as crystalline plates 
containing small proportions of silicon and of aluminium. Its 
density is 4.15, and it is less fusible than silicon. 

Zirconium forms but one chloride, ZrCP, which may be formed 
by the action of chlorine on a highly-heated mixture of zirco- 
nium oxide and charcoal. It is a white solid, which dissolves 
in water with the formation of a hydrated oxychloride. 



THORIUM. 423 

Zirconium Oxide, ZrO^, the only known oxide, may be 
obtained from the native silicate zircon. The pulverized min- 
eral is fused with potassium hydroxide, then exhausted with 
hydrochloric acid, and the solution evaporated to dryness to 
separate the silica. The residue is dissolved in water, and the 
solution treated with ammonia, which precipitates hydrates of 
iron and zirconium. The precipitate is treated with oxalic 
acid, and ferric oxalate dissolves, while insoluble zirconium 
oxalate remains and yields zirconium oxide when calcined. 

Zirconium oxide is a white powder, of a density between 
4 and 5, according to the temperature of calcination. It is 
insoluble in acids, with the exception of hydrofluoric and 
sulphuric acids. It is infusible, and becomes highly incan- 
descent when heated. It is an excellent substitute for lime 
in the oyxhydrogen light, and is extensively used for the 
Welsbach light. 

Zirconium oxide acts both as a base and as the anhydride 
of an acid forming salts analogous to the silicates. 



THORIUM. 

Th = 231.5 

Thorium was discovered by Berzelius, in 1828, in the min- 
eral thorite, from Norway, in which it exists as an impure 
silicate. It occurs in the same form in orangeite, and associ- 
ated with cerium and lanthanum as phosphate in monazite. 

The metal has been obtained only as a gray powder by heat- 
ing its chloride with potassium or sodium. It does not decom- 
pose water, but burns when heated in the air. 

Thorium Oxide, ThO^, may be prepared from thorite by 
boiling the powdered mineral with hydrochloric acid, evapor- 
ating to dryness, and exhausting the residue with boiling water. 
After passing hydrogen sulphide through the filtrate, the clear 
liquid is precipitated with ammonia. The precipitate is dis- 
solved in hydrochloric acid and treated with potassium sul- 
phate ; a double sulphate crystallizes out, and this is redissolved 
in water and thorium hydroxide, Th(OH)*, precipitated by 
the addition of ammonia. 



424 ELEMENTS OP MODERN CHEMISTRY. 

The oxide obtained by igniting the hydroxide is hard, gray- 
ish, and translucent. It is infusible, and is not reduced by 
charcoal or attacked by fused alkalies. It is dissolved only 
by boiling sulphuric acid. When heated to incandescence it 
emits a more brilliant light than zirconia, and is the most 
valued earth for the Welsbach light. 

Thorium Chloride, ThCP, is prepared by passing chlorine 
over a heated mixture of the oxide with charcoal. It then 
volatilizes in short, white prisms. It is deliquescent, and a 
solution of its hydrate may be obtained by dissolving thorium 
hydrate in hydrochloric acid. This hydrate contains ThCl* -{- 
8H^0, and, when heated, is decomposed with formation of 
hydrochloric acid. 

Thorium forms oxysalts replacing four atoms of hydrogen 
in the acids. 



PLATINUM. 

Pt = 193.41 

Natural State and Treatment of Platinum Ores. — The 

only compound of platinum found in nature is the arsenide 
PtAs'^ known as sperrylite^ which is isomorphous with pyrite 
and is found in the nickel-mines of Sudbury, Ontario. Com- 
mercial platinum is derived from the native metal, which is 
generally found in alluvial sands. Its principal deposits are 
in the Ural Mountains, Brazil, and California. The plati- 
num ore, extracted from the sand by washing, contains, in- 
dependently of 73 to 86 per cent, of platinum, various other 
metals, such as iridium, palladium, rhodium, osmium, ruthenium, 
gold, iron, and copper ; an alloy of osmium and iridium, and 
various minerals, such as titaniferous iron, chrome iron, pyrites, 
etc. The ore is well washed to remove the sand, and treated 
with dilute aqua regia which dissolves the gold, iron, and cop- 
per ; it is then heated with concentrated hydrochloric acid and 
nitric acid is gradually added. The aqua regia dissolves the 
platinum and certain of its accompanying metals, leaving the 
osmium and iridium. A solution of ammonium chloride is 
added to the filtered liquid ; it produces an abundant pre- 
cipitate of ammonium and platinum double chloride, which 



PLATINUM. 425 

generally contains a small quantity of ammonium and iridium 
double chloride. This precipitate is calcined at a dull-red 
heat, and leaves a dull-gray, spongy residue. It is spongy 



To give coherence to this sponge and convert it into a mal- 
leable and ductile metal, it is reduced to powder in a wooden 
mortar and triturated with enough water to convert it into a 
perfectly homogeneous paste. This paste is introduced into a 
slightly-conical cylinder of brass or iron, and compressed first 
with a wooden piston, then by a steel rod. The compression 
is finished by the aid of a hydraulic press, and the slightly- 
conical cylinders so formed are heated to whiteness and forged 
under the hammer, as iron is forged. 

To obtain perfectly pure platinum, the metal is dissolved 
in aqua regia, the excess of acid evaporated, and the residue 
heated to 150° ; the iridium is thus converted into Ir^CP 
which remains in solution when the platinum is precipitated 
with ammonium chloride. 

H. Sainte- Claire Deville and Debray extracted the metal 
by simple fusion of the ore. The fusion is effected in a len- 
ticular cavity cut in two large masses of quick-lime, placed 
one above the other. A current of illuminating gas is di- 
rected into this furnace, and the combustion is supported by 
a continual supply of oxygen. 

Properties of Platinum. — Platinum has a grayish-white 
lustre. It melts only at the highest attainable temperatures. 
The density of the cast metal is 21.1 ; that of the forged metal 
21.5. It softens at a white heat, and can then be forged and 
welded like iron. 

The experiments of H. Deville and Troost have shown that a 
red-hot platinum tube allows hydrogen to pass through its pores. 

Platinum has the curious property of condensing gases on its 
surface, and this property is the cause of certain chemical phe- 
nomena that were formerly attributed to mere contact of the 
metal. 

If a morsel of platinum-sponge be introduced into a small 
jar filled with an explosive mixture of oxygen and hydrogen, 
the gases will combine instantly, with explosion. 

This property is most highly developed in platinum-blach, 
for in this form the metal exists in an extreme state of 
division. It may be prepared by reducing a solution of 
platinic chloride by zinc ; or platinum dichloride may be boiled 

36* 



426 ELEMENTS OF MODERN CHEMISTRY. 

with potassium hydroxide, and alcohol or a solution of sugar 
gradually added to the liquid, which must be continually 
stirred. The platinum is precipitated as a black powder. 

Platinum is unaltered by the air. It is not attacked by 
either nitric, hydrochloric, or sulphuric acid, even boiling. It 
dissolves in aqua regia. The alkaline hydroxides attack it at 
high temperatures on contact with the air. It is the same 
with the alkaline nitrates. 

There are two oxides of platinum, a monoxide, PtO, and a 
dioxide, PtOl 

CHLOKIDES OF PLATINUM. 

These are the more important compounds of platinum. 
There are two, a dichloride, PtCP, and a tetrachloride, PtCl*. 

Platinum dichloride is obtained by cautiously heating the 
tetrachloride to 200"^. Chlorine is disengaged, and after cool- 
ing, the residue is exhausted with boiling water, which leaves 
an olive-green powder, constituting the dichloride. When 
ammonia is added to a solution of platinum dichloride in 
hydrochloric acid, a green, crystalline powder separates after 
some time. It is called green salt of Magnus, and contains 

PtCP-f 2NH^ 

It may be regarded as the dichloride of platinoso-diammonium. 

Pt" 

It is derived from two molecules of ammonium chloride by 
the substitution of an atom of diatomic platinum for two atoms 
of hydrogen. 

Platiniim tetrachloride, or platinic chloride, PtCl*, is 
formed when platinum is dissolved in aqua-regia. A red- 
brown solution is obtained, which, after concentration and cool- 
ing, deposits red-brown needles of hydrated platinic chloride. 
The crystals lose their water when heated, and are converted 
into a dark, red-brown mass, which constitutes the anhydrous 
chloride PtCl*. This body absorbs moisture when exposed to 
the air. It is very soluble in water, alcohol, and ether. 

If a solution of ammonium chloride be added to a solution 
of platinic chloride, a yellow, crystalline precipitate of plati- 
num and ammonium double chloride is immediately formed. 



r2 r NICP 



OTHER METALS OF THE PLATINUM GROUP. 427 

This body is but little soluble in cold water, but more soluble 
in boiling water, from which it is deposited in microscopic, 
regular octahedra. It is almost insoluble in alcohol. It contains 

PtCP.2NH^Cl 

A yellow, crystalline precipitate of double chloride of plati- 
num and potassium is obtained, in the same manner, on adding 
a solution of platinic chloride to a solution of a potassium salt, 
if the liquids be not too dilute. 

PtCl*.2KCl 



OTHER METALS OF THE PLATINUM 
GROUP. 

Rhodium, ruthenium, palladium, iridium, and osmium are 
associated with native platinum, and are usually extracted from 
platinum residues. They are fusible with great difficulty, and 
not readily attacked by acids. Their separation from each other 
is accomplished by tedious and complicated reactions, but, with 
the exception of ruthenium and rhodium, they possess certain 
valuable properties which have found for them applications in 
the arts. They combine with oxygen, forming a series of 
feeble bases, and a series of acid oxides. With the exception of 
the volatile oxides of ruthenium and osmium, these compounds 
are decomposed by heat into metal and oxygen. 

Rhodium is less fusible than platinum, and almost insoluble 
in aqua-regia, which, however, dissolves it if it be alloyed with 
the baser metals. Its specific gravity is 12.1. It forms oxides 
RhO, Rh20^ and RhO^ and a chloride Rh^CP. 

Ruthenium is a hard metal, having a density of 12.26 at 
0°, and is more infusible than iridium. It is hardly attacked 
by boiling aqua-regia. One of its most interesting compounds 
is a volatile oxide RuO*. Its chloride has the composition 
Ru^CP. 

Palladium has the lowest melting-point of the group of 
platinum metals, fusing at about the same temperature as 
wrought iron. Its specific gravity at ordinary temperatures is 
11.4. When a bright piece of* the metal is heated in the air, 
its surface becomes tarnished from the formation of a film of 
oxide, but at a higher temperature this oxide is again reduced 



428 ELEMENTS OF MODERN CHEMISTRY. 

to metal. The remarkable facility with whicli palladium ab- 
sorbs hydrogen has already been mentioned (page 61). Pal- 
ladium forms three oxides, Pd^O, PdO, and PdO^ and two 
chlorides, PdCP and PdCl*. 

Iridium occurs with the platinum ores in grains of platin- 
iridium and osmiridium. Its fusing-point is the highest after 
osmium and ruthenium. It is very hard, and next to osmium 
it has the highest specific gravity of any substance known, its 
density being 22.38. An alloy of platinum and iridium con- 
taining ten per cent, of the latter metal is as hard and elastic 
as steel, unalterable in the air, and less fusible than platinum. 
It is used for the points of gold pens. 

Iridium forms two oxides, Ir^O^ and IrO^, and two chlorides, 
Ir^CP and IrCh 

Osmium has been obtained in cubical or rhombohedral 
crystals having a density of 22.48. Its melting-point is about 
2500°. When strongly heated in the air it burns into a vola- 
tile oxide, OsO'^, which is dangerously poisonous. The native 
alloy, osmiridium, is used for the points of gold pens. Two 
chlorides are known, OsCP and OsCl*. 



ORGANIC CHEMISTRY. 



GENERAL IDEAS UPON THE CONSTITUTION 
OF OEGANIC COMPOUNDS. 

Organic chemistry studies the history of the compounds 
of carbon. The most simple of these are the gases carbon 
monoxide and carbon dioxide ; each contains but a single atom 
of carbon. In this respect they resemble the inflammable gas 
which is disengaged from the mud of marshes ; it contains one 
atom of carbon combined with four atoms of hydrogen. 

The gas hydrogen dicarbide or ethylene, which has already 
been mentioned, contains two atoms of carbon united with four 
atoms of hydrogen. A great number of compounds are known 
which contain only carbon and hydrogen, and they are called 
hydrocarbons or carburetted hydrogens. The atoms of carbon 
are aggregated in them, together with the atoms of hydrogen. 
Other elements are often added to the preceding, forming 
molecules more or less complex. The carbon atoms form as it 
were the framework, and the carbon compounds possess pecu- 
liar properties precisely on account of the great facility with 
which the atoms of carbon accumulate in one and the same 
molecule, and link themselves in some manner one to another. 
The following developments will give some idea of the mode 
of formation and the structure of organic molecules. 

The most Simple Organic Compounds. — Their Composi- 
tion proves Carbon to be a Tetratomic Element. — The most 
simple of the hydrocarbons is marsh gas. 

When this gas is submitted to the action of chlorine, one or 
more atoms of hydrogen may be removed from it ; they com- 
bine with the chlorine and are disengaged in the form of hy- 
drochloric acid gas. The curious fact, first noticed by Dumas, 
is then observed, that each atom of hydrogen which is removed 
is replaced by an atom of chlorine. This substitution gives 

429 



430 ELEMENTS OF MODERN CHEMISTRY. 

rise to a series of chlorinated compounds, wliicli present tlie 
most simple relations with marsh gas. The latter contains only 
carbon and hydrogen. The chlorine compounds derived from 
it by substitution, form with it the following series : 

CH* marsh gas, or methane. 

CH^Cl monochloromethane (methyl chloride). 

CH2C12 dichloromethane (methylene chloride). 

CHC13 trichloromethane (chloroform). 

CCl* tetrachloromethane (carbon tetrachloride). 

In each of these compounds a single atom of carbon is united 
with four monatomic atoms. We have seen that the atoms of 
chlorine and hydrogen are equivalent as regards their power 
of combination. In the preceding compounds, the sum of the 
atoms of hydrogen and chlorine which are combined with one 
atom of carbon is invariably four, and this number cannot be 
exceeded. But two atoms of a monatomic element may be re- 
placed by one atom of a diatomic element. One atom of car- 
bon, which unites with four atoms of hydrogen or chlorine, 
may unite with two atoms of oxygen to form carbon dioxide 

CO"' 

and this compound is saturated like those preceding, for one 
atom of oxygen is equivalent to two atoms of hydrogen or 
chlorine. In carbon monoxide, CO'', the affinity of carbon is 
not satisfied ; hence this gas will unite directly with an atom 
of oxygen to form carbon dioxide, or with two atoms of chlo- 
rine to form carbonyl chloride. 

CO'^CP 

In ammonia, one atom of nitrogen is combined with three 
atoms of hydrogen ; nitrogen is triatomic ; hence it may replace 
three atoms of hydrogen. A body is known which represents 
marsh gas, in which three atoms of hydrogen are replaced by 
one atom of nitrogen. This is the dangerous poison known as 
prussic or hydrocyanic acid, and the composition of which is 
represented by the formula 

CN'"H 

In all of the compounds which have just been mentioned a 
single atom of carbon is invariably united to a number of ele- 
ments of which the sum of the atomicities is four, and never 
more nor less than that number. It is then reasonable to 
conclude that in them carbon plays the part of a tetratomic 



INTRODUCTION TO ORGANIC CHEMISTRY. 431 

element. This important fact, first exposed by Kekule, can be 
clearly understood if we represent tbe preceding atomic formulae 
in a graphic manner, that is, by symbols so arranged as to show 
the reciprocal relations of the atoms and their mutual satura- 
tion. In these formulas a saturated atomicity is indicated by 
a line of union, two atomicities by two lines, etc. 

H H H CI 

H-C-H H-C-Cl Cl-C-Cl Cl-C-Cl 



I I I 

H H CI 



h 



Marsh gas. Monocliloro- Tnchloroiiietliane. Carbon 

methane. (Chloroform.) tetrachloride. 

CI 
0=C-0 Cl-C-0 H-CEN 

Carbon dioxide. Carbonyl chloride. Hydrocyanic acid. 

There exists a very volatile, ethereal liquid, which represents 
marsh gas, in which one atom of hydrogen is replaced by iodine. 
It is the body known as methyl iodide, CH^I. 

If this body be heated for a long time in a sealed tube with 
a solution of potassium hydroxide, potassium iodide will be grad- 
ually formed, and the solution will contain a volatile, spirituous 
liquid which can easily be separated by distillation, for it boils 
at 66°. It is the same body which constitutes the most vola- 
tile of the liquids which are formed in the destructive distilla- 
tion of wood ; it is called wood spirit, and its chemical name is 
methyl alcohol. 

The reaction by which it is formed is very simple. The 
iodine of the methyl iodide combines with the potassium ; but 
when this iodine is removed, the carbon remains united to but 
three atoms of hydrogen. It is no longer saturated, and it 
therefore combines with the oxygen and hydrogen which were 
united with the potassium in the potassium hydroxide. 

CH^I -f KOH = CHIOH + KI 

It will be seen that the atom of oxygen alone does not com- 
bine with the group CH^, which is called methyl. It is accom- 
panied by an atom of hydrogen, with which it remains united 
in the new compound, which is called methyl hydroxide or 
methyl alcohol. As has been said, this oxygen replaces the 
iodine in the iodide of methyl, but as it possesses two atomici- 
ties, and the carbon already united with H^ has only one free 
atomicity, the atom of oxygen can only fix upon the carbon by 



432 ELEMENTS OF MODERN CHEMISTRY. 

one of its atomicities ; the other remains saturated by the atom of 
hydrogen. The latter is then drawn into the combination, and is 
united, not to the carbon, but to the oxygen. The reaction takes 
place as if the atom of iodine were replaced by the group hy- 
droxyl (OH) which is monatomic. Hence the relations between 
the atoms in methyl hydroxide are represented by the formula 

H 

H-CJ-COH)' 

H 

If we compare the constitution of the three bodies CH^Cl, 
CH^I, CH^(OH), we notice that they contain a common ele- 
ment, namely, the group CH^, which is united to chlorine, to 
iodine, or to hydroxyl. Besides this, experiment has shown 
that methyl iodide can be transformed into the hydroxide. 
The group methyl hence presents a certain stability and can 
pass from one combination to another. This is expressed by 
saying that it is a radical. 

If methyl iodide be heated with an aqueous solution of 
ammonia, among the products formed will be found the hydri- 
odide of a base which represents ammonia in which one atom 
of hydrogen is replaced by the group methyl. Potassium 
hydroxide sets this base at liberty. At ordinary temperatures 
and pressures, it constitutes a gas, very soluble in water and 
possessing a strong ammoniacal odor. It is methylamine. The 
reaction by which it is formed is as follows : the iodine with- 
draws one atom of hydrogen from the ammonia, which atom 
of hydrogen is replaced by the group CH^. 

QWl + NH=^ = CH\NH^).HI. 

Methylamine hydriodide. 

In methylamine then, the fourth atomicity of the carbon 
atom is saturated by nitrogen, but as this element is triatomic 
it brings into the combination two atoms of hydrogen which 
saturate its two other atomicities. It may then be said that 
in methylamine the fourth atomicity of carbon is saturated by 
the group NH^ This is expressed in the following formulae. 

H H 

H-C-N=H^ = H-C1-(NH7 

H 

Methylamine. 



i 



INTRODUCTION TO ORGANIC CHEMISTRY. 433 

Formation of Hydrocarbons containing Several Atoms 
of Carbon. — The preceding compounds contain but a single 
atom of carbon, but starting with one of these compounds we 
may produce more complicated organic molecules containing 
several carbon atoms. 

If methyl iodide be heated with sodium in sealed tubes, 
sodium iodide is formed, and a gas, a hydrocarbon, is confined 
under great pressure in the tubes. This gas escapes, and may 
be collected, when the drawn-out points of the tubes are opened 
in the blow-pipe flame. It is dimethyl, and has been formed 
according to the following reaction : 

2CH3I -f Na^ = C^H« + 2NaI 

Methyl iodide. Dimethyl, or ethane. 

Two molecules of methyl iodide have entered into the reac- 
tion, and the whole of the carbon of these two molecules is 
found in one molecule of the hydrocarbon, C^H^ = (CH^)^, 
which results. 

On losing their iodine the two methyl groups combine to- 
gether. One of the carbon atoms attracts the other, exchanging 
with it the fourth atomicity set free by the loss of the iodine. 
Hence the iodine of one of the molecules of methyl iodide has 
been replaced by the carbon of the other, which fixes upon the 
group CH^ by a single one of its atomicities, and at the same 
time brings into the combination the three atoms of hydrogen 
which saturate the other three atomicities. This is expressed 
in the following formulae : 

H H H H 

H-C-H H-C-I H-C-C^H 

I I II 

H H HH 

Methane (methyl hydride). Methyl iodide. Dimethyl (ethyl hydride or ethane). 

The mode of generation of this new hydrocarbon, which 
contains two atoms of carbon, is worthy of consideration. It 
results from the substitution of a methyl group for one atom of 
hydrogen in methyl hydride. One atom of carbon, accompa- 
nied by three atoms of hydrogen, fixes upon another atom of 
carbon of which it completes the saturation. By this exchange 
of atomicities each of the carbon atoms retains only three afiin- 
ities which are satisfied by three atoms of hydrogen. The 
two methyl groups, CH^ -f- CH^ = C^H*, are then united by 
their carbon atoms, and are held together by the affinity of 
T cc 37 



434 ELEMENTS OP MODERN CHEMISTRY. 

carbon for carbon. In methyl hydroxide the group hydroxy! is 
bound to the group CH^ by the affinity of carbon for oxygen. 
In methylamine, the group NH^ is united to the group CH^ by 
the affinity of carbon for nitrogen. In dimethyl, it is carbon 
which is united to carbon. This has before been expressed by 
saying that the atoms of this element possess a faculty to accu- 
mulate in one and the same molecule. 

It is in this curious property that must be sought the reason 
for the existence of those innumerable compounds, more or less 
rich in atoms of carbon, which constitute the immense field of 
organic chemistry. 

But it is important to study by new examples this mode of 
formation of organic compounds. 

Dimethyl, which we have seen is produced by the action of 
sodium upon methyl iodide, is also known as ethyl hydride. If 
one of its atoms of hydrogen be replaced by an atom of chlo- 
rine, ethyl chloride, C'H^Cl, is obtained. Ethyl iodide, C'H^I, 
represents ethyl hydride, in which one atom of hydrogen has 
been replaced by iodine. 

If a mixture of methyl iodide and ethyl iodide be heated 
with sodium, among the products of the reaction will be found 
a gas containing C^H® ; this gas is methyl-ethyl, and it results 
from the combination of methyl, CH^, with the group ethyl, 
C^H^ It represents ethyl iodide in which the atom of iodine 
has been replaced by a methyl group, the carbon of the latter 
group being fixed by one of its atomicities to one of the carbon 
atoms of the group C^H^. 

In the same manner, by heating a mixture of propyl iodide, 
C^H^I, and methyl iodide with sodium, we may add to the 
propyl group, C^H^, a new atom of carbon escorted by its three 
atoms of hydrogen. 



HH 


HHH 


HHHH 


H-C-C-I 


H-C-C-C-H 


H-C-C-C-C-H, etc. 


1 1 
HH 

Ethyl iodide. 


i 1 1 
HHH 

Methyl-ethyl (propane). 


1 1 1 1 
HHHH 

Methyl-propyl (butane). 



Nothing prevents the continuation of these additions of car- 
bon to incomplete hydrocarbons, that is, to the residues of the 
subtraction of iodine from the saturated iodides, of which the 
following are the names and formulae : 

CffI C^H^I C^H^I C*H«I C^H^^I, etc. 

Methyl iodide. Ethyl iodide. Propyl iodide. Butyl iodide. Amyl iodide. 



INTRODUCTION TO ORGANIC CHEMISTRY. 435 

The following hydrocarbons would then be formed succes- 
sively : 
CH3-CH3 C2H5_CH3 C5H7-CH3 C*H9-CH» CSHH-CHs, etc. 

Methyl-metliyl Methyl-ethyl Methyl-propyl Methyl-butyl Methyl-amyl 
(Ethane). (Propane). (Butane). (Pentane). (Hexane). 

In all of these cases, the atoms of carbon united together 
form, as it were, a continued chain, and the atoms of hydrogen 
are grouped around them as satellites. 

Homologous Bodies. — Very simple relations exist between 
the hydrocarbons of which we have just studied the mode of 
formation. They form a series of which each member differs 
from the preceding by the addition of CH^ These relations 
will appear clearly if the formulse already given be replaced 
by the crude formulse : 

C H* methane. 
C'W ethane. 
C^H^ propane. 
C'W^ butane. 
C^H^^ pentane. 

This group of hydrocarbons constitutes what is called the 
homologous series of marsh gas, or the series C"H^"+l 

Many other series are known, the terms of which are related 
to each other in the same manner, and the bodies which form 
part of them may present the greatest differences in composition. 
Sometimes they contain only carbon and hydrogen. Again, 
they may contain oxygen or nitrogen in addition to these ele- 
ments ; in this case the former elements are united to carbon by 
one or more of their atomicities, as has already been indicated. 

In any organic body whatever, if an atom of hydrogen united 
with carbon be replaced by a methyl group, CH^, the superior 
hoTYiologue of that body is obtained, that is, the compound which 
differs from the original body by the addition of CH^. There 
is a great resemblance in physical and chemical properties 
between such homologues. 

Some of these homologous series will be indicated farther on. 

Composition and Classification of Organic Compounds. 
— The elements carbon, hydrogen, oxygen, and nitrogen are 
the most common constituents of organic compounds. Those 
which occur in the vegetable kingdom consist, for the most 
part, of the three first named, although there are also many 
nitrogenous bodies of vegetable origin. Animal matter, as a 



436 ELEMENTS OF MODERN CHEMISTRY. 

rule, contains all four of tlie elements mentioned and not in- 
frequently sulphur and phosphorus in addition. But nearly 
all of the other elements can be introduced artificially into 
organic compounds ; it is thus with chlorine, bromine, iodine, 
arsenic, boron, silicon, and a great number of the metals. 

In uniting with carbon, in different manners and in various 
proportions, these elements form an innumerable multitude of 
compounds, each of which has a fixed composition and definite 
properties. These bodies constitute the chemical species, so to 
say. When submitted to the action of reagents, all may be 
modified in a thousand manners, and transformed into each 
other. Sometimes their composition is simplified, one or more 
carbon atoms being removed from the chain. Sometimes it is 
complicated by synthesis ; that is, the addition of new atoms 
of carbon. 

All these bodies contain carbon, and are distinguished : 

1. By the number of carbon atoms contained in the 
molecule. 

2. By the nature and arrangement of the other atoms com- 
bined with the carbon. 

3. By the arrangement of all the atoms in the molecule. 

The facts relative to the atomic composition of organic com- 
pounds are obtained by elementary analysis and by the deter- 
mination of the molecular weight. 

ELEMENTARY ANALYSIS. 

The object of elementary analysis is the determination of 
the nature and proportion of the elements contained in any 
given organic body. We can give here but a summary descrip- 
tion of the processes employed, considering only those which 
have for object the determination of carbon, hydrogen, and ni- 
trogen. Oxygen is almost invariably estimated by difference. 

The percentages of carbon and hydrogen are determined in 
one operation. In case nitrogen or other elements are present, 
the relative quantity of each of these must be ascertained 
by separate operations. 

Determination of Carbon and Hydrogen. — To determine 
the proportion of carbon and hydrogen contained in 100 parts 
of any given organic substance, the carbon is converted into 
carbon dioxide, which is collected and weighed, and the hydro- 
gen into water, which is condensed and weighed. These opera- 
tions are conducted according to a method devised by Liebig. 



ELEMENTARY ANALYSIS. 437 

For this end, tlie organic matter, previously dried with care, is 
burned with an excess of cupric oxide. The operation is exe- 
cuted in a combustion-tube of hard glass, which is wrapped with 
a spiral of metallic foil to prevent it from bending and swell- 
ing under the influence of the heat. Well-dried cupric oxide 
is introduced into the tube, then an intimate mixture of the 
substance to be analyzed with a large excess of the same oxide, 
and the remainder of the tube is filled with pure cupric oxide. 

The tube is then placed in a combustion furnace, and its 
open extremity is put in communication with (1) an U tuhe,jg 
(Fig. 120), containing fragments of calcium chloride in the first 
branch, and pumice-stone impregnated with sulphuric acid in 
the second; (2) a tube with five bulbs, h, called Liebig's potash 
bulbs, containing a concentrated solution of potassium hydroxide, 
and followed by a small U tube, i, containing pumice-stone im- 
pregnated with potassium hydroxide in the first branch, and frag- 
ments of potassium hydroxide in the second. These different 
tubes have first been accurately weighed. When the appa- 
ratus is arranged, the combustion-tube is slowly heated, com- 
mencing at the extremity B, and gradually extending the heat 
so that each part of the tube is successively heated to redness. 
The water formed by the combustion is collected in the first 
U tube, the carbon dioxide is absorbed by the potassium hy- 
droxide in the bulbs. When the operation is terminated, a rub- 
ber tube connected with an oxygen reservoir is slipped over the 
drawn-out end of the combustion tube which is then crushed 
within the rubber tube. An excess of oxygen is then passed 
through the combustion-tube, in order to drive out the traces 
of carbon dioxide and aqueous vapor which it contains at the 
end of the combustion. It is then only necessary to weigh the 
water tube and the carbon dioxide tubes. The increase in 
weight which is found indicates, on one hand, the quantity of 
water, and on the other the quantity of carbon dioxide, pro- 
duced by the combustion of the organic matter. The compo- 
sition of water and of carbon dioxide being known, it is easy 
to deduce from the weight of these two bodies the quantities 
of hydrogen and carbon contained in the analyzed substance, 
and consequently the proportion of these two elements con- 
tained in 100 parts of that substance. 

Fig. 120 represents the operation towards its close : the 
combustion-tube is in the gas-furnace, B, and communicates, 
on the right with the tubes g, h, i, destined to receive the pro- 

37* 



438 



ELEMENTS OF MODERN CHEMISTRY. 




ELEMENTARY ANALYSIS. 



439 



ducts of the combustion, on the left with two large U tubes, 
the first of which is filled with pumice-stone impregnated with 
potassium hydroxide to absorb traces of carbon dioxide, the 
second with pumice-stone saturated with sulphuric acid to 
absorb moisture. Through these tubes is passed the oxygen, 
at the close of the operation, to expel the last portions of carbon 
dioxide and vapor of water. 

When the substance contains carbon, hydrogen, and oxygen, 
the proportion of oxygen is the difference between the total 
percentage of carbon and hydrogen found and 100. 




EiG. 121. 

Determination of Nitrogen. — Nitrogen may be determined 
by several methods. One of these is to burn a given weight 
of the nitrogenous substance with an excess of cupric oxide. 
The carbon of the substance is converted into carbon dioxide ; 
the hydrogen is converted into water ; the nitrogen is disen- 
gaged. The gases, nitrogen and carbon dioxide, are received 
in a graduated jar standing on the mercury-trough and con- 
taining potassium hydroxide. The carbon dioxide is absorbed, 
the nitrogen remains. At the close of the operation, the last 
traces of nitrogen are expelled by a current of carbon dioxide. 
The volume of nitrogen is then measured, and its weight de- 
duced from its volume (Dumas). 

Another process (Fig. 121) consists in decomposing the 
nitrogenous organic matter with an alkali at a high tempera- 
ture. By this means all of the nitrogen is converted into 
ammonia. The substance is intimately mixed with soda lime, 
that is, lime impregnated with caustic soda. The mixture is 
heated to redness in a tube of hard glass, and the ammonia is 



440 ELEMENTS OF MODERN CHEMISTRY. 

received in a tube with three bulbs containing dilute hydro- 
chloric acid. Ammonium chloride is formed ; when the opera- 
tion is terminated, the liquid containing the salt is mixed with 
a solution of platinic chloride. It is then evaporated and 
exhausted with alcohol, which leaves the platinum and ammo- 
nium double chloride, 2(NH*C1) + PtCl*. The latter is col- 
lected upon a tared filter, then washed and dried. From its 
weight is calculated that of the nitrogen contained in the 
organic substance (Will and Varrentrapp). 

The ammonia disengaged may also be received in 10 cubic 
centimetres of a normal solution of sulphuric acid, that is, an 
acid liquor containing a known quantity of sulphuric acid in 
a determined volume. 

The strength of this acid is determined by neutralizing 10 
c.c. of it with a dilute alkaline solution of known strength and 
noting the volume of the latter required. The same operation 
is repeated with the 10 c.c. of which the acid has been par- 
tially neutralized by the ammonia. The quantity of ammonia 
corresponds to the difference between the volumes of the alka- 
line liquid employed in these two operations, and can easily be 
calculated by simple proportion (Peligot). 

Still another mode of estimating nitrogen, devised by Kjel- 
dahl, depends upon the fact that the nitrogen of organic bodies 
is quantitatively converted into ammonia, when such bodies 
are heated with strong sulphuric acid. After an excess of caus- 
tic soda has been added to neutralize the acid, the ammonia 
liberated is distilled off and estimated as above described. 

Determination of the Molecular Weight of Organic Sub- 
stances. — Elementary analysis permits the determination of 
the centesimal composition of organic substances. This is 
indispensable, but it is insufficient for the establishment of 
their atomic composition, that is, the number of atoms of car- 
bon, hydrogen, oxygen, and nitrogen which are contained in a 
single molecule of a given organic compound. But if the 
weight of the molecule be known (hydrogen being taken as 
unity), it is easy to deduce the atomic composition from the 
figures given by elementary analysis, as will be seen by the 
following example. By elementary analysis it is found that 
100 parts of acetic acid contain 

Carbon 40. 

Hydrogen 6.67 

Oxygen 53.33 

100.00 



ELEMENTARY ANALYSIS. 441 

On the other hand, methods which will be described have 
shown that the molecular weight of acetic acid is 60 ; that is to 
say, the total weight of the atoms of carbon, hydrogen, and 
oxygen contained in a molecule of acetic acid, is 60. 

Hence by the following proportions : 

If 100 parts acetic acid contain 40 of carbon, 60 parts contain x. 
" " " 6.67 of hydrogen, '' " y. 

" " " 53.33 of oxygen " « z. 

From which, x = 24; y = 4 ; 2 = 32. 
Hence 24 represents the weight of the atoms of C contained in a molecule 

of acetic acid. 
4 represents the weight of the atoms of H contained in a molecule of acetic 

acid. 
32 represents the weight of the atoms of contained in a molecule of acetic 
acid. 

By dividing these numbers by the weights of the respective 
atoms, the number of atoms of C, H, and contained in a 
molecule of acetic acid is readily determined. 

24 -=- 12 = 2 atoms of carbon. 
4 -i- 1 = 4 " hydrogen. 

32 -^ 16 = 2 " oxygen. 

Hence the formula of acetic acid is C^H*0^. 

After the analysis of an organic substance has been made, it 
is only necessary to determine the molecular weight in order 
to establish the atomic composition. Several processes are em- 
ployed for this determination, of which the most convenient, 
when applicable, is the determination of the vapor density. 

The vapor density is most conveniently determined by 
measuring the volume occupied by the vapor of a known 
weight of the substance and dividing this weight by that of 
an equal volume of hydrogen at the same temperature and 
pressure. An apparatus devised by Victor Meyer and shown 
in Fig. 122 is generally employed for this purpose. The 
inner vessel b is heated by the vapor of some liquid whose 
boiling-point is considerably higher than that of the given 
substance. When the temperature becomes constant, which 
is indicated by air ceasing to escape through /, a graduated 
tube filled with water is inverted over the mouth of /. A 
small stoppered tube filled with a weighed quantity of the 
substance has been supported by the glass rod c h, and is 
caused to fall by slightly withdrawing the rod. On reaching 
the bottom the substance instantly volatilizes, and the vapor 
displaces an equal volume of air of the same temperature 



442 



ELEMENTS OP MODERN CHEMISTRY. 



and pressure ; this escapes througli /, and is collected and 
measured in the graduated tube, and its volume under normal 
conditions calculated by aid of the formula 



-^ 




(1 + .003665 i) 760' 

in which v is the measured volume, P the pressure under 

which the air is measured, li 
the tension of aqueous vapor 
at the temperature, ^, at which 
the air is measured. The 
weight of an equal volume 
of hydrogen is then divided 
into the weight of substance 
taken, and the quotient is the 
required density. The vapor 
density of acetic acid com- 
pared to hydrogen is thus 
found to be 30 ; the molecular 
weight corresponding would 
be 60. 

Other methods must be em- 
ployed for determining the 
molecular weights of sub- 
stances that cannot be vapor- 
ized without decomposition, 
and advantage has been taken 
of the fact that in dilute solu- 
tions substances behave in 
many respects like gases or 
vapors. The most accurate 
and most convenient of the 
methods based on this prin- 
ciple is the cryoscopic method, 
devised by E-aoult. When 
a dilute solution of a com- 
pound is cooled to its freezing- 
point, the latter is found to be 
lower than the freezing-point 
of the pure solvent. Within 
certain limits of concentration this depression of the freezing- 
point is directly proportional to the weight of the substance 



-b 



Fig. 122. 



ELEMENTARY ANALYSIS. 



443 



dissolved, and has been shown by Raoult to be proportional 
to the number of molecules of the substance dissolved in a 
certain weight of the solvent, and independent of the nature 
of the substance. Hence, if several substances in equimo- 
lecular proportions be dissolved in like quantities of the 
same solvent, each will produce the same depression of the 
freezing-point. The depression produced by the number of 
grammes corresponding to the molecular weight of the sub- 
stance in 100 grammes of the solvent is called the molecular 
depression of the solvent ; different solvents have different 
molecular depressions. If this constant be known for any 
solvent, the molecular weight of a substance may be de- 
duced by determining the depression pro- 
duced by a known proportion of the 
substance. If c be the depression ob- 
served when p grammes of the sub- 
stances are dissolved in I grammes of the 

solvent, then ^ 



I 



grammes of the sub- 



stance must be dissolved in 100 grammes 
of solvent to produce the same depression. 
If T represent the molecular depression 
of the solvent and Jif the required molec- 
100 p 

j^^^lOOpT 



ular weight, 



31 = c : T, and „_ 



Ic 



Fig. 123 represents an apparatus, de- 
scribed by Beckmann, for accurate meas- 
urements of the depression of the freezing- 
point, e is a wide tube having a capacity 
of about 25 c. c. up to the lateral tube, 
and closed by a cork carrying a stout 
platinum stirring-rod and a thermometer 
graduated to .01°. e is surrounded by a 
wider tube, d, which is fixed in the metal 
lid of the vessel cr, which contains a liquid 
cooled to about 5° below the freezing-point of the solvent. 
The annular space between e and d contains air, which pre- 
vents too rapid cooling. 

A weighed quantity, about 15 grammes, of the solvent is 
introduced into e, and constantly stirred with the rod until it 




Fig. 123. 



444 ELEMENTS OF MODERN CHEMISTRY. 

begins to freeze ; as soon as the temperature becomes con- 
stant the freezing-point is noted. The tube e is now with- 
drawn and the solvent allowed to melt, when the tube is 
replaced, and a weighed quantity of the substance is dropped 
in through the lateral tube. The freezing-point of the solu- 
tion is noted, and the difference between the two readings is 
the depression. 

When for any reason neither of the methods already de- 
scribed can be applied to determine the molecular weight, a 
chemical method may be employed. We will again con- 
sider acetic acid. Salts may be formed with this acid, and 
we know that these salts contain one atom of metal. We may 
then analyze silver acetate. 100 parts of that salt contain 
64.67 parts of silver. This fact being known, it is easy to deter- 
mine the molecular weight of silver acetate. Since the latter 
contains one atom of silver, we can conclude, if 64.67 parts of 
silver are contained in 100 parts of silver acetate, 108 parts 
of silver, that is, one atom, are contained in x parts of silver 
acetate ; whence x = 167. This number represents the molec- 
ular weight of silver acetate. That of acetic acid may be de- 
duced by substituting the atomic weight of hydrogen for that 
of silver, which gives for the molecular weight of acetic acid 60. 

Analogous operations and reasoning permit the determina- 
tion of the molecular weights of bodies playing the part of 
bases. They are combined with an acid, the molecular weight 
of which is known, and the composition of the combination 
furnishes the data for the calculation of the molecular weight 
of the base. This method can be applied in a large number 
of analogous cases, and presents a great generality. 

Determination of Meltings-Points and Boiling-Points. — 
A knowledge of the color, density, crystalline form, tempera- 
tures of freezing and boiling, and other physical constants 
of carbon compounds, is of importance not only as means of 
identification, but in the development of the theory which 
shall throw light on the influence of composition on proper- 
ties. Many carbon compounds are fusible and volatile with- 
out decomposition, and the exact temperatures at which these 
changes of state occur are highly characteristic, and are 
determined with great care. 

For the determination of the melting-point, a small quan- 
tity of the substance in fine powder is introduced into a 
capillary tube closed at one end, which is then attached by 



ISOMERISM, METAMERISM, POLYMERISM. 



445 



tlie side of a chemical thermometer so that the substance 
shall be on the same level as the bulb ; a caoutchouc band 
or a fine platinum wire keeps the capillary tube in position. 
The thermometer is then supported over a beaker, h (Fig. 
124), in which the thermometer bulb and substance are just 
immersed in a liquid of high boiling-point, such as sulphuric 
acid or paraffin oil. The whole is cautiously heated while agi- 
tating by the stirrer s, and the temperature of fusion is noted. 





Fig. 124. 



Fig. 125. 



Boiling-points are determined by distilling a small quantity 
of the substance in a " Wurtz distilling tube" (Fig. 125), 
which is a small, long-necked flask, /, with a side tube, s, 
through the cork of which passes the thermometer t. It is 
advisable that the neck of the flask should be so long that 
the whole mercurial column at the given boiling-point is 
surrounded by the vapor. 



ISOMERISM, METAMERISM, POLYMERISM. 

Elementary analysis demonstrates that many bodies which 
differ in their physical and chemical properties, possess ex- 
actly the same centesimal composition. Such bodies are said 
to be isomeric. Two kinds of isomerism exist. Sometimes 
the isomeric bodies contain the same number of similar atoms 
in molecules of the same size, and diff"er only by the arrange- 
ment of these atoms ; sometimes they contain similar atoms 

38 



446 ELEMENTS OF MODERN CHEMISTRY. 

united in the same proportion, but not in tlie same number, 
in molecules of unequal magnitude. 

In both cases the centesimal composition is the same, for it 
depends only on the relative number of the atoms. 

The first kind of isomerism constitutes metamerism; the 
second, polymerism. Acetic acid and methyl formate are an 
example of two metameric bodies. Each contains 2 atoms of 
carbon, 4 of hydrogen, and 2 of oxygen ; their molecules are 
equal in size, but different in atomic structure. The latter fact 
may be expressed by the following formulae : 

C'^HSQ.OH acetic acid 
CH30.0CH methyl formate 

The first expresses that acetic acid contains a group of atoms, 
C^ffO, acetyl, which is united with hydroxyl, OH ; the second, 
that methyl formate contains a group, CHO, formyl, which is 
united with oxymethyl, CH^O. The difference in the atomic 
arrangement becomes evident, if the preceding formulae be 
developed in the graphic manner. 

0-H 0-CH^ 

I I 

c=o c=o 

1 I 

CH« H 

Acetic acid. Methyl formate. 

The theory of atomicity has thus enabled to discover the 
atomic structure of a great number of combinations, and to 
explain numerous isomerisms. 

Acetic acid and glucose or grape-sugar present an example 
of^ polymerism. Both contain the atoms of carbon, hydrogen, 
and oxygen, united together in the same proportions, but the 
molecule of the second contains three times as many of each 
a^ that of the first. 

C2H402 acetic acid. 
3 X C2H402 = C6H1206 glucose. 

Among the more important and better known cases of po- 
lymerism, may be mentioned the numerous hydrocarbons which 
present the centesimal composition of ethylene or olefiant gas, 
and which differ from it by the regularly increasing number of 
their atoms of carbon and hydrogen. These bodies form the 
following homologous series : 

C2H* ethylene. C^Iie propylene. C*H8 butylene. C^Hio amylene. 



FUNCTIONS OF ORGANIC COMPOUNDS. 447 

Within recent years chemists have been called upon to ex- 
plain still another kind of isomerism ; the atoms constituting 
the molecules of different substances may be not only the 
same in kind and number, they may be even similarly grouped. 
Thus there are three acids known to have the formula COOH. 
CH(OH).CH(OH).COOH, but they differ markedly in cer- 
tain physical properties. In such cases it is now generally 
held that the differences are caused by different arrangement 
of the atoms in space. (See page 614.) 

FUNCTIONS OF OKGANIC COMPOUNDS. 

In the study of mineral chemistry it has been seen that 
bodies present great differences in properties, according to their 
composition. Some are simple and apt to enter into combina- 
tion ; others are compound and indifferent ; the first are more 
or less energetic in their affinities, the others saturated and 
satisfied. In one case, we have examined either more or less 
powerful acids or bases, some of which are hydroxides, as 
potassa and soda, others are oxides, as those of lead and 
silver. In the other case we have studied the salts result- 
ing from the union of the former bodies. 

In organic chemistry we again encounter various kinds of 
bodies which have different functions, according to their com- 
position. 

It may be said, in a general manner, that the properties of 
compound bodies depend upon the nature of the atoms and 
their arrangement in the molecule. In treating of isomerism, 
the influence of the latter condition has been indicated ; that 
of the former is still more powerful. 

Water and potassium hydroxide are both constituted, and in 
an analogous manner, of three elementary atoms. Each con- 
tains one atom of oxygen united to two monatomic atoms. 

HOH KOH 

Water. Potassium hydroxide 

But what a difference in their properties ! But may not 
this be expected when it is considered that one contains the 
energetic metal potassium, in the place occupied in the other 
by the light gas hydrogen ? Is the difference between potash 
and water greater than that between potassium and hydrogen ? 



448 ELEMENTS OP MODERN CHEMISTRY. 

And if for tlie two atoms of hydrogen we substitute two atoms 
of chlorine, is it not to be expected that hypochlorous oxide 

Cl-O-Cl 

the molecule of which is similar in structure to that of water. 



shall differ from the latter in its properties as much as chlo- 
rine differs from hydrogen ? It is thus that the nature of the 
elements contained in compound bodies is the dominant condi- 
tion in the manifestation of their properties. 

The following considerations are of a nature to demonstrate 
the truth of this proposition inasmuch as concerns organic 
compounds : 

MONATOMIC RADICALS. 

Saturated Hydrocarbons. — The hydrocarbons belonging 
to the series of marsh gas are all saturated. Consider, for 
example, C^H® ; all of the atomicities of two atoms of carbon 
are satisfied by the union of the latter together and with six 
atoms of hydrogen. 

HH 

H-C-C-H 

I I 
HH 

Ethane, or ethyl hydride. 

It is the same with all of its homologues ; the hydrides of 
propyl, butyl, amyl, etc., are all saturated hydrocarbons, as will 
be seen by developing the formula of any one of them, pentane, 
for example : 

HHHHH 

I I I I I 

H-C-C-C-C-C-H 

I I I I I 

HHHHH 

Pentane, or amyl hydride. 

All of these bodies are incapable of fixing other elements 
by direct addition, but they may be modified by substitution, 
that is, one or several of their atoms of hydrogen may be 
replaced by other elements. 

Monatomic Chlorides, Bromides, and Iodides. — By the 
reaction of bromine upon any of the hydrocarbons, we may 



MONATOMIC RADICALS. 449 

obtain compounds containing an atom of bromine in the place 
of an atom of hydrogen. 

C'H« + Br^ = C'WBr + HBr 

Ethane. Ethyl bromide. 

A saturated and indifferent hydrocarbon is thus converted 
into a bromide. 

The corresponding chloride and iodide exist, possessing the 
same constitution as the primitive hydrocarbon, and forming 
with it the following series : 

C2H6 ethane, 
C2H5C1 ethyl chloride. 
C2H5Br ethyl bromide. 
C2H5I ethyl iodide. 

To the other hydrocarbons correspond chlorides, bromides, 
and iodides analogous to the preceding. Thus, the following 
groups are known : 

CH* methane. C^Hi^ pentane. 

CH301 methyl chloride. C^HUCl amyl chloride. 

CH^Br methyl bromide, C^HiiBr amyl bromide. 

CH3I methyl iodide, C^HUI amyl iodide. 

All of these bodies may be made to undergo the most varied 
transformations. They may be attacked by a number of re- 
agents, to which they present a hold, as it were, since the chlo- 
rine, bromine, and iodine which they contain are gifted with 
powerful affinities. 

The residues resulting from the subtraction of the chlorine, 
bromine, or iodine then enter into other combinations. It will 
be remarked that these residues represent the saturated hydro- 
carbons from which one atom of hydrogen has been removed. 

CH^ = CH^Br — Br, or CH* — H 
C^H^ = C^ffBr — Br, or C'W — H 
C^H^i = C^H"Br — Br, or C^H^^ — H 

The atoms of carbon contained in these residues, CH^, C^H^, 
and C^H", are no longer entirely saturated, since CI, Br, I, or 
H has been removed, elements which satisfied one atomicity. 
Therefore, these residues are capable of entering other com- 
binations, but as they possess only one free atomicity, they can 
only saturate one when they combine. This is expressed by 
saying that they play the part of monatomic or univalent 
radicals. The chlorides, bromides, and iodides from which 
they are derived contain but one atom of the halogen. 
dd 38* 



450 ELEMENTS OE MODERN CHEMISTRY. 

Alcohols. — The neutral hydroxides corresponding to the 
preceding chlorides, bromides, and iodides, are called alcohols. 

If ethyl iodide be heated for a sufficiently long time with 
potassium hydroxide, potassium iodide will be formed, and 
the alkaline liquid will contain alcohol which may be 
separated. 

This body is ethyl hydroxide, and is formed according to 
the following reaction : 

C^H^I + KOH == KI 4- C^HIOH 

Ethyl iodide. Ethyl hydroxide. 

It is formed, as is seen, by double decomposition. The 
potassium having removed the iodine from the ethyl iodide, 
the monatomic residue C^H^ combines with the monatomic 
residue OH. Alcohol is then the hydroxide which corresponds 
to the iodide, C^H^I, and to the hydrocarbon, C^H^ Analo- 
gous hydroxides correspond to the other hydrocarbons of the 
same series ; they constitute the series of monohydric alcohols, 
and may be defined as derived from the saturated hydrocarbons 
by the substitution of the group hydroxyl for one atom of 
hydrogen. The alcohols now known are numerous : the follow- 
ing are some of them : 

CH3.0H methyl hydroxide, or methyl alcohol. 

C^H^.OH ethyl hydroxide, or ethyl alcohol. 

C^H'^.OH propyl hydroxide, or propyl alcohol. 

C*H9.0H butyl hydroxide, or butyl alcohol. 
C^Hii.OH amyl hydroxide, or amyl alcohol. 
C^H^^.OH hexyl hydroxide, or hexyl alcohol. 
C^H^s^OH heptyl hydroxide, or heptyl alcohol. 
C^Hi'^.OH octyl hydroxide, or oetyl alcohol. 

Each member of this series differs from that which follows 
by — CHI All are allied by analogous properties. These two 
conditions characterize homologous bodies. The alcohols of 
which the general formula is C"H^''"*"^OH, form one of the most 
important series of homologues. 

If one of these alcohols be heated with hydrochloric, hydro- 
bromic, or hydriodic acid, water will be formed and the alcohol 
will be converted into a monatomic chloride, bromide, or iodide. 
In this reaction the hydroxyl, OH, is replaced by chlorine, 
bromine, or iodine. 

C^H^OH -f HCl = WO H- C^H^Cl 

Ethyl hydroxide. Ethyl chloride. 

The bodies thus formed are the monatomic chlorides, bro- 



MONATOMIC RADICALS. 451 

mides, or iodides before considered. These experiments show 
the relations which exist between the latter compounds and the 
corresponding hydroxides, which are the alcohols. 

Monobasic Acids. — Acetic acid, which exists in vinegar, is 
a derivative of alcohol, of which it is one of the products of 
oxidation. It is formed under many conditions, one of which 
is the oxidation of alcohol vapor on contact with platinum 
black and the air. 

C'ff.OH -{. 0' = C'H^O.OH + H^O 

Alcohol. Acetic acid. 

In this reaction an atom of oxygen removes two atoms of 
hydrogen to form water, and the place of these two atoms of 
hydrogen is filled by another atom of oxygen. The group 
ethyl, C^H^, thus becomes the group acetyl, C^H'''0, and if 
alcohol be the hydroxide of ethyl, acetic acid is the hydroxide 
of acetyl. We can account for this reaction by developing the 
formulae of alcohol and acetic acid according to the principles 
before explained. 

HH HO 

H-C-C-OH + 0^ =:= H-C-C-OH + H^O 
I I I 

HH H 

Alcohol. Acetic acid. 

In alcohol, the second carbon atom is combined with two 
atoms of hydrogen and with one group hydroxyl, while in 
acetic acid it is combined with an atom of oxygen and a group 
hydroxyl. 

Acetic acid contains two atoms of carbon united together, 
and combined, the one with H^, the second with and OH. 
It is thus formed of a group CH^ united to a group CO-OH 
= CO^H. There exist many other acids analogous to acetic 
acid, and derived, like it, by oxidation of the monatomic alco- 
hols of the series C"H"^"+^OH. All of these acids contain 
a hydrocarbon group analogous to methyl, combined with the 
group CO^H :=: CO-OH. The hydrogen of the latter group 
can be readily replaced by an equivalent quantity of metal. 
This hydrogen is said to be strongly basic, and all of the organic 
acids which contain a single group, CO^H, united to a hydro- 
carbon group, are monobasic like acetic acid. The homologues 
of the latter form the followino; series : 



452 ELEMENTS OF MODERN CHEMISTRY. 

C H2 02 = H -C02H formic acid. 
C2 H* 02 = C H3 -C02H acetic acid. 
C3 H6 02 = C2H5 -C02H propionic acid. 
C4 H8 02 = C3H7 -C02H butyric acid. 
C5 H10O2 ^ C*H9 -C02H valeric acid. 
C6 H1202 = C5H11-C02H caproie acid. 
07 H1402 = C6H13-C02H cenanthic acid. 
C8 H1602 = Cmi5-C02H caprylic acid. 
C9 H1802 _ C8H17-C02H pelargonic acid. 
C10H2002 = C9H19-C02H capric acid, etc. 

The first series of formulae indicates simply the nature and 
number of atoms contained in the acids of the series CH^'^O^. 
They are empirical formulae. The second series gives certain 
indications upon the relations existing between these atoms. 
They are rational formulae, and when developed so as to ex- 
press the relations between all of the atoms, they become 
constitutional formulae. 

Compound Ethers. — The compound ethers are combina- 
tions which represent acids of which the hydrogen has been 
replaced by a hydrocarbon group. 

If one of the alcohols of the preceding series, ordinary alco- 
hol, for example, be heated for a long time with acetic acid, 
water will be formed, and a volatile, neutral liquid possessing an 
agreeable odor may be separated from the product ; this sub- 
stance is ethyl acetate, or acetic ether. It is formed according 
to the following reaction : 

Alcohol. Acetic acid. Ethyl acetate. 

On comparing this compound with alcohol, we find that it 
is formed by substitution of the group C^H^O, the existence of 
which is admitted in acetic acid, and which is called acetyl, 
for one atom of hydrogen in alcohol ; and this atom of hydro- 
gen which is replaceable by acetyl is that which is united to the 
oxygen in alcohol, — that which forms a part of the hydroxyl 
group. The other atoms of hydrogen, those which constitute 
part of the group C^H^, cannot be replaced by acetyl. 

All of the acids can form with alcohol, and indeed with all 
of the alcohols, compounds analogous to ethyl acetate, and 
these combinations are called compound etheo-s, or ethereal salts. 
The property possessed by the alcohols of etherifying acids is 
general and characteristic of this class of compounds. Alco- 
hols which require for etherification but a single molecule of 



KETONES. 453 

an acid analogous to acetic acid are called monohydric. Many 
exist which are not included in the preceding series. 

Aldehydes. — Acetic acid is not the only product of the 
oxidation of alcohol. There is another compound interme- 
diate between these two ; it results from the action of a single 
atom of oxygen upon the molecule of alcohol, which thus loses 
two atoms of hydrogen without other change. The new com- 
pound is aldehyde. 

CWO + = H^O + C^H^O 

Alcohol. Aldehyde. 

It is a very volatile liquid having a great tendency to become 
oxidized and converted into acetic acid. It forms crystalline 
combinations with the alkaline acid-sulphites. To the other 
alcohols of the series C"H^"+^0, and other acids of the series 
Qnjj2nQ2^ corrcspoud compounds analogous to aldehyde by their 
composition and by their properties. They form the following 
series : 

C^H^O aldehyde or acetaldehyde. 

C^H^O propionic aldehyde. 

C^HSQ butyric aldehyde. 

C5H10O valeric aldehyde, etc. 

Ketones. — When calcium acetate is submitted to dry distil- 
lation a neutral, volatile liquid is obtained, having a peculiar 
aromatic odor, and known by the name acetone. 



Q2JJ3Q2 

Calcium acetate. Acetone. Calcium carbonate. 

To the other acids of the acetic acid series correspond bodies 
analogous to acetone, and forming with it a homologous series. 
These ketones are related by properties and composition to the 
aldehydes. Like the latter, they form crystalline combinations 
with the alkaline acid-sulphites. It may be considered that 
while aldehyde is the hydride of acetyl, acetone is the methyl- 
ide of acetyl, and that in general the ketones are derived by 
the substitution of a hydrocarbon group, analogous to methyl, 
for an atom of hydrogen in the aldehydes considered as hy- 
drides. 

CH^-CO-H CH^-CO-CH^ 

Aldehyde (acetyl hydride). Acetone (acetyl methylide). 

Hence, acetone contains two methyl groups united to a group, 
CO (carbonyl). Its mode of formation justifies this conclusion, 



454 ELEMENTS OF MODERN CHEMISTRY. 

as shown in the following equation, in which the constitu- 
tional formula of acetic acid is employed : 

CH3-C0 0>^^ = CaCO^ + CH3-CO-CH3 

Calcium acetate. Calcium carbonate. Acetone. 

Diketones. — Free acid radicals. — Like the methyl group, 
the radicals of the monobasic acids cannot exist alone, but 
only in combination with other atoms or groups. Just as two 
methyl groups unite to form dimethyl or ethane, so two acetyl 
groups are combined in diacetyl. Such compounds contain- 
ing two carbonyl groups are called diketones. 
CH3CO.COCH3 diacetyl 
CH3CO.COC2H5 acetyl propionyl, etc. 

Chlorides of Acid Radicals. — A compound is known in 
which the acetyl group is united with chlorine. Acetyl chlo- 
ride, C^H'O.Cl, is a monatomic chloride, like ethyl chloride 
C'^H^Cl, from which it is distinguished by the strongly electro- 
negative nature of its radical. 

If acetyl chloride be poured into water, it disappears in a 
short time with development of heat and the formation of 
acetic and hydrochloric acids. 

C2H30.C1 -f H20 = C^H^O.OH + HCl 

Acetyl chloride. Acetic acid. 

To acetyl chloride correspond other chlorides which contain 
radicals of acids analogous to acetic acid. When they are 
treated with water they yield hydrochloric acid and the acids 
corresponding to their radicals. 

C3H50.C1 C3H50.0H 

Propionyl chloride. Propionic acid. 

C^H^O.Cl C*H70.0H 

Butyryl chloride. Butyric acid. 

Amides. — If acetyl chloride be treated with ammonia, am- 
monium chloride will be formed, together with a solid, neu- 
tral, nitrogenized body called acetamide. 

C^HSCCI + 2NH3 = NH*C1 + C^HSQ.NH^ 

Acetyl chloride. Acetamide. 

There are many other compounds similar to acetamide, and 
known by the name amides. They are formed by the action 
of ammonia upon organic halides analogous to acetyl chloride. 
They are also formed by the action of heat upon the ammonia- 
cal salts of the monobasic acids. The latter compounds then 
lose one molecule of water, and are converted into amides. 
C^H^O.ONH* = C5H90.NH2 + H^O 
Ammonium valerate. Valeramide. 



COMPOUND AMMONIAS. 455 

Acetamide may be regarded as ammonia in wliieli an atom 
of hydrogen lias been replaced by the radical acetyl. 
( H ( C^H^O r C^H^O 

Ammonia. Acetamide. Valeramide. 

Compound Ammonias, or Amines. — If ethyl iodide be 
heated with ammonia, one of the products of the reaction will 
be the hydriodide of a base derived from ammonia by the sub- 
stitution of an ethyl group for an atom of hydrogen. 

C^H^I + NIP = (C^H5)NHIHI 

Ethyl iodide. Ethylamine hydriodide. 

In this reaction, other ethylated bases are formed, independ- 
ently of ethylamine, among which must be mentioned diethyl- 
amine and triethylamine. All present the most striking anal- 
ogy to ammonia. They may be regarded as ammonia in which 
one, two, or three atoms of hydrogen have been replaced by 
one, two, or three ethyl groups. 

Ammonia. 

The other alkyl groups, C°H^''+^, can in the same manner 
replace one or more atoms of hydrogen in ammonia. The 
products are bases having constitutions analogous to those 
of the ethyl bases. They are called amines, or compound 
ammonias. 

It is necessary that the signification of the formulae above 
given and those that are to follow shall be clearly understood. 
They are examples of typical notation, and indicate the rela- 
tions of the compounds with the type ammonia. 

N"' ] H 
(H 

The brace joining the three hydrogen atoms signifies that 
the whole three are united to a single atom of triatomic nitro- 
gen, with which each exchanges one atomicity; this may be 
expressed by writing the formula for ammonia thus : 



C^H^) 


C'W) 


C^H^) 


H y-N 


C'W [ N 


C'W Y N 


Hj 


H) 


C'W) 


Ethylamine. 


Diethylamine. 


Triethylamine. 



456 



ELEMENTS OF MODERN CHEMISTRY. 



What, then, takes place when one or more atoms of hydro- 
gen are replaced by a group like ethyl ? The latter exchanges 
one atomicity with the nitrogen atom, precisely as the hydro- 
gen atom did, and combines with the nitrogen by one of the 
atoms of carbon of the group ethyl, CH^-CH^, which requires 
the satisfaction of one atomicity. 

This is clearly expressed in the following graphic formulae : 
H H 



N-CH^- 

I 
H 



CH^ 



N-CH^-Cff 
CH^-CH^ 

Ethylamine. Diethylamine, 

However, such formulae would be too cumbrous for ordinary 
use, and our formulae must be more condensed. 

/C^H^ /C^m 

N^H N^C'H^ NCC^'Hsy 

^H ^H 

Ethylamine. Diethylamine. Triethylamine. 

Phosphines. — Arsines. — Stibines. — There exist several se- 
ries of combinations belonging to the same type as the com- 
pound ammonias, but in which the nitrogen is replaced by 
phosphorus, arsenic, or antimony. These compounds are de- 
rived from the hydrogen compounds of phosphorus, arsenic, 
and antimony by the substitution of one or more alkyl' groups 
for one or more atoms of hydrogen. 



H^ cm'-) 


C^H^-) 


C'H^") 


H VP H fP 


C'H^ [ P 


C^H^ [ P 


HJ H ) 


H) 


cw) 


Hydrogen phosphide. Ethylphosphiue. 


Diethylphosphine. 


Triethylpliosphine 


H) CH^) 


CW) 


cnn 

CH^' [ As 
CH^' j 


H V As H V As 


CW [ As 


HJ HJ 


CI j 


Hydrogen arsenide. Methylarsine. 


Dimethylarsine 


Trimethylarsine. 


H) 


chloride. 


C^H^^ 


XT ( Ol. 




C^H^ [ Sb 
C'H^) 






Hydrogen antimonide. 




Triethylstibine. 



Organo-metallic Compounds. — Ethyl and its congeneric 
radicals, methyl, amyl, etc., can enter into combination not 
only with nitrogen, phosphorus, arsenic, etc., of which they 
saturate one or more atomicities, but with a large number of 



ORGANO-METALLIC COMPOUNDS. 457 

metals. Thus, zinc, wliicli is diatomic, can combine with two 
ethyl groups to form zinc ethyl. 



Mercury, also diatomic, can unite with one or two ethyl or 
methyl groups, etc. In the second case, the new combination 
is saturated ; in the first, it is monatomic, (Hg"C^H^)', and re- 
quires for saturation an atom of a monatomic element, or a 
monatomic group, iodine, for example. 

Hg |(..H^ Hg I J 

Mercur-ethyl. Mercur-monethyl iodide. 

Bismuth, which is triatomic, can fix three ethyl groups. 

Bi'" \ cm' 
(cm' 

Bismuth-ethyl. 

Stanno-tetrethyl is formed by the union of four ethyl groups 
with one atom of tetratomic tin. 

If the four atomicities of tin be not all satisfied, non-satu- 
rated compounds may be formed. 

Sn'' ] y,,^, -Sn-^ C'^H^ or -Sn-^C^H^ 

Stanno-diethyl. Stanno-triethyl. 

Stanno-diethyl is known in the free state, but stanno-triethyl 
doubles its molecule as soon as it is set at liberty, combining 
with itself, as it can combine with iodine. 

ISn'-(C^H^)^ (C^H5)"^Sn^^-Sn'-(C'H5)3 = Sn^CC^IF)^ 

stanno-triethyl iodide. Sesquistannethyl. 

Non-saturated compounds are apt to combine with other 
elements or radicals. Stanno-tetrethyl, which is saturated, does 
not possess this faculty. 

The bodies just mentioned belong to the class of organo- 
metalUc compounds. Their study is of great importance in 
the history of the atomicity of the metals, that is, their power 
of saturation. The theoretical considerations concerning them 
have been discussed by Frankland, Baeyer, and Cahours. 
u 39 



458 



ELEMENTS OF MODERN CHEMISTRY. 



Monatomic Radicals. — From the preceding summary may 
be understood the position occupied in organic chemistry by 
certain groups containing carbon, groups that are distinguished 
as monatomic because they can manifest but a single atomicity. 
Only a single monatomic atom or group is wanting that all of 
the carbon atoms contained in these groups may be entirely 
saturated. These groups of atoms or radicals cannot exist in 
the state of liberty, but they can pass from one compound to 
another, replacing a single atom of hydrogen or other mon- 
atomic element^ and consequently pla^dng the part of that ele- 
ment in the new combination. This is expressed by saying 
that these groups act as monatomic radicals. 

To indicate the constitution of the combinations containing 
such groups, and especially the metamorphoses that they may 
undergo by exchanging these radicals by double decomposition, 
it is convenient to designate the latter by expressions written 
separately in the formula and distinct from those for the 
other elements. The composition of all of the bodies which 
have just been reviewed may be represented by very simple 
formula3, by comparing them to hydrogen compounds, such as 
free hydrogen, or hydrochloric acid, water, and ammonia. The 
notation then assumes a typical form, exceedingly clear for the 
interpretation of the majority of reactions. 

The following are the typical formulae for the combinations 
that have been considered : 



Type HH, 


Type g jo. 


Type H ^N. 


(eff)Cl 


(c-h;.)„ 


H fN 


Ethyl chloride. 


Ethyl hydrate. 


Ethylamine. 


(C^H^O)Cl 






Acetyl chloride. 


Ethyl hydroxide. 


Diethylamine. 


(C^H30)H 


(C^^jo 






{(JW) ) 


Aldehyde. 


Acetic acid. 


Triethylamine. 


(C^H^O)(CH0 




H fN 
H) 


Acetone. 


Ethyl acetate. 


■ Acetamide. 



POLYATOMIC RADICALS. 459 



POLYATOMIC RADICALS. 

If chlorine and defiant gas, or ethylene, be mixed in equal 
volumes, both gases disappear and are converted into an oily 
substance, which was formerly called Dutch liquid. This body 
results from the combination of a molecule of ethylene with a 
molecule (two atoms) of chlorine. It is ethylene chloride. 

C^H^ + CP = C^H^CP 

Ethylene. Ethylene chloride. 

If the constitution of ethylene gas, C^H*, be compared with 
that of the saturated hydrocarbon ethane, C^H®, which like the 
former contains two atoms of carbon, it will be noticed that it 
contains two atoms of hydrogen less. 

C'H^ — H^ = C'H* 

In ethylene the six atomicities of the pair of carbon atoms 
are not saturated. Hence that gas can absorb directly two 
atoms of chlorine or bromine to form a saturated compound. 
HH H H HH 

H-C-C-H -C-C- Cl-C-C-Cl 

II II II 

HH HH HH 

Ethane. Ethylene. Ethylene chloride. 

It is a diatomic radical, or alkylene, and it can exist in the 
free state because until other atoms are presented to satisfy the 
atomicities of the two atoms of carbon those two atoms are 
bound together by a double affinity. Thus, H^C=CH'. One 
of these bonds is loosed when the ethylene manifests its affini- 
ties and enters directly into combination, because the affinity 
of carbcr for chlorine or "uch an element is greater than its 
affinity for carbon Ethylene is the first of a numerous class. 
The following bodies form with it the homologous series CH^"" •. 

C2H4 ethylene. 
C^H^ propylene. 
C^HS butylene. 
C5H10 amylene. 
C6H12 hexylene. 
C^i* heptylene. 
C8H16 octylene. 
C9H18 nonylene. 
C10H20 decylene, etc. 



460 ELEMENTS OF MODERN CHEMISTRY. 

All of these bodies are able to fix directly two atoms of 
chlorine or bromine. When they enter into combination, they 
take the place of two atoms of hydrogen. They can pass by 
double decomposition from one compound to another, and their 
combinations may undergo various metamorphoses analogous 
to those already indicated. 

Dihydric Alcohols, or Glycols. — The glycols are compounds 
in which the two atomicities of the alkylenes are saturated 
by two hydroxyl groups. The two atoms of bromine in ethy- 
lene bromide, C^H^Br^, may be replaced by two hydroxyl groups 
(OH), and the resulting combination is ethylene hydroxide. 

The two atoms of hydrogen united to the oxygen in the 
hydroxyl groups in glycol may both be replaced by acid radi- 
cals analogous to acetyl, just as the single atom of hydrogen in 
the single hydroxyl group of a monatomic alcohol may be 
replaced by an acid radical. This is characteristic of a dihydric 
alcohol. 

To ethylene hydroxide, or ordinary glycol, correspond the 
hydroxides of the other hydrocarbons homologous with ethy- 
lene. The following glycols are known : 

C^H^jol glycol. 

r OTT 
C^HS j Qjj propyleneglycol. 

C4H8 I ^ butyleneglycol. 

C5H10 I Qg amyleneglycol. 



C6H12 1 ^ hexyleneglycol, etc. 



Around each of these bodies are grouped a great number of 
derivatives, among which we can only consider the ethers^ acids, 
and compound ammonias. 

Ethers of the Glycols. — The ethers of the glycols result 
from the substitution of alcoholic or acid radicals for the hydro- 
gen of the groups OH. One or both of these hydrogens may 
be thus replaced, and the following examples will illustrate the 
constitution of the compounds so formed : 

^ ^ 1 OH ^^ 1 O.C2H5 ^^ I OH ^^ 1 O.C2H30 

Monethylic glycol. Diethylic glycol. Glycol monacetate. Glycol diacetate. 



POLYATOMIC RADICALS. 461 

Hydroxy-acids and dibasic acids result from the oxida- 
tion of the glycols. Their formation and constitution may 
be understood by developing the formulae of the hydrocarbons 
which constitute the radicals of these glycols. Ordinary 
glycol may yield two acids by oxidation, the first resulting 
from the substitution of an atom of oxygen for two atoms 
of hydrogen, the second from the substitution of two atoms 
of oxygen for four atoms of hydrogen. The following for- 
mulae express the constitution and derivation of these com- 
pounds : 

CH^ CH^Br Cff.OH CHIOH CO.OH 

CH^ bwBr CHIOH CO.OH C!O.OH 

Ethylene. Ethylene bromide. Glycol. Glycolllc acid. Oxalic acid. 

Grlycollic acid and oxalic acid are, therefore, both derived 
from the same dihydric alcohol ; but the former is monobasic 
because it contains but a single atom of hydrogen that can be 
replaced by a metal. The second is dibasic, for it contains 
two atoms of hydrogen that are replaceable by an equivalent 
quantity of metal. This basic hydrogen is that which forms 
part of the group CO'^H. Oxalic acid is composed simply of 
two groups -CO'^H ; it is dibasic. Glycollic acid contains but 
one, and it is consequently monobasic. The hydrogen united 
to the oxygen in the group -CH^OH is called alcoholic hydro- 
gen ; it may be replaced by an acid radical, but it cannot be 
easily replaced by a metal. All bodies containing a group 
CHI OH are alcohols, and all bodies containing a group 
CO.OH are acids. The alcohols and acid are thus defined by 
their constitution. Grlycollic acid is at the same time an alco- 
hol and an acid, — an hydroxy-aeid, — for it contains both a 
group CH'^.OH and a group CO.OH. 

There exists a series of acids homologous with glycollic acid, 
and another series homologous with oxalic acid. Both series 
are derived from the higher dihydric alcohols. 

Diatomic Ammonias, or Diamines. — Compounds exist 
which hold the same relation to the dihydric alcohols as ethyl- 
amine and its homologues to the monohydric alcohols. Such 
a compound is ethylene-diamine. Its relations with ethylene 
chloride and glycol are expressed by the following formulae : 

C^H*<^} G"^'<OH ^'^'<NW 

Ethylene chloride. Glycol. Ethylene-diamine. 

39* 



462 ELEMENTS OF MODERN CHEMISTRY. 

Trihydric and Polyhydric Alcohols. — There are alcohols 
containing three or more hydroxyl groups; glycerol, for ex- 
ample, is a trihydric alcohol. It contains a radical, C^ff, 
which is triatomic, since it is derived from the saturated hydro- 
carbon C^H^ by the subtraction of three atoms of hydrogen. 
Erythritol is a tetrahydric alcohol ; it contains the tetratomic 
radical C*H^ = C^H^"— H^ Lastly, the sweet, sugar-like sub- 
stance derived from manna, and known as mannitol, is a hexa- 
hydric alcohol. There are many analogous bodies containing 
three or more hydroxyl groups, but in no case does the num- 
ber of these groups exceed that of the carbon atoms in the 
molecule. The following formulae represent the composition 
and the functions of the polyhydric alcohols that have been 
mentioned : 

C^H^'" (0H)3 C*H«^ (OH)* C^H«- (0H)« 

Glycerol. Erythritol, Maunitol. 

Around these bodies are grouped the numerous correspond- 
ing derivatives, ethers, acids, etc. 

The above considerations show that the neutral hydroxides, 
called alcohols, are highly important in themselves and on 
account of the derivatives which attach to them. Hence the 
elements of a natural classification of organic compounds are 
deduced. 

COMPOUNDS OF CYANOGEN. 

Gay-Lussac gave the name cyanogen to the radical of prussic 
or hydrocyanic acid, which was discovered by Scheele in 1782. 
This radical is composed of one atom of carbon and one atom of 
nitrogen. In hydrocyanic acid it is united with hydrogen ; in 
the cyanides it is combined with the metals. 

H(CN)' K(CN)' Hg^'CCNy 

Hydrocyanic acid. Potassium cyanide. Mercury cyanide. 

The preceding compounds may be compared with the corre- 
sponding chlorides : 

HCl KCl HgCP 

Hydrochloric acid. Potassinra chloride. Mercuric chloride. 

It is somewhat remarkable that potassium cyanide is iso- 
morphous with potassium chloride. 

In the preceding compounds, cyanogen, which is composed of 
an atom of carbon and an atom of nitrogen, plays a part anal- 
ogous to that of chlorine. It is a monatomic radical ; nitrogen, 



CYANOGEN. 463 

which is triatomic, can saturate only three of the four atomici- 
ties which reside in an atom of carbon. Hence there remains 
one free atomicity, and cyanogen can act as a monatomic radi- 
cal, -cen. 

All of the compounds of cyanogen are prepared from potas- 
sium ferrocyanide, or yellow prussiate of potash, which is 
described on page 468. 

CYANOGEN. 

(CN)2 = Gy2 

Formation. — Cyanogen occurs in small quantities in the 
gases from blast-furnaces. Nitrogen and carbon combine 
together with difficulty, but their direct union takes place in 
presence of potassium or potassium carbonate at a high tem- 
perature. When nitrogen gas is passed over an incandescent 
mixture of carbon and potassium carbonate, potassium cyanide 
is formed. A larger yield of cyanide is obtained if the nitrogen 
is replaced by ammonia gas. Also, if ammonia gas is passed 
over incandescent charcoal in a porcelain tube, ammonium 
cyanide is formed, and may be condensed in crystals in a cooled 
receiver (Kuhlmann). 

C + 2NH3 r= NH*.CN -|- H^ 

Ammonium cyanide. 

Cyanogen is also formed by the dehydration of ammonium 
oxalate, when that salt is treated with phosphoric anhydride. 
This reaction allows cyanogen gas to be regarded as the nitrile 
of oxalic acid. A nitrile is a cyanide which may be converted 
into an acid by hydration, with elimination of ammonia, by the 
action of an alkaline hydroxide. 

CO.ONH' CN 

CO.ONH* CN ^ 

Ammonium oxalate. Cyanogen. 

Preparation. — Mercury cyanide is heated in a small retort 
fitted with a delivery -tube. The mercury volatilizes, and a gas 
is disengaged which may be collected over mercury. This^is 
a free cyanogen. It has separated from the mercury, which 
is condensed in the dome of the retort. There remains in the 
retort a solid brown mass which possesses the same composition 
as cyanogen, and is known Vi^ paracyanogen. 
Hg(CN)^ = (CN)^ -f Hg 



464 ELEMENTS OF MODERN CHEMISTRY. 

Composition and Properties. — Cyanogen is a colorless gas, 
possessing a strong odor of bitter almonds. It may be easily 
liquefied by a pressure of 4 atmospheres or a temperature of 
— 25°. Its density is 1.8064 compared to air, or 26 compared 
to hydrogen. 

In the cyanide of mercury the metal was combined with 
two groups (CN), which unite together when they separate 
from the mercury, and remain combined together in the gas 
which is disengaged. The latter contains CN combined with 
CN. Its formula is : 

NC-CN = (CN)2 = Cf 

2 volumes of this gas contain two atoms of carbon and two 
atoms of nitrogen. 

This composition may be demonstrated by eudiometric analy- 
sis. 

2 volumes of cyanogen and 4 volumes of oxygen are intro- 
duced into a mercury eudiometer. On the passage of an electric 
spark there is a flash of blue light, and the volume of the gas 
is not changed. If a solution of potassium hydrate be now 
passed into the eudiometer, the six volumes of gas will be 
reduced to two. 

4 volumes of CO^ are formed; 

2 volumes of N remain. 

2 volumes of cyanogen then contain the carbon contained in 2C02, that 
is, C2, and N^. 

This is expressed by saying that the formula of cyanogen, C^N^ = Cy^, 
corresponds to 2 volumes. 

On contact with flame, cyanogen takes fire and burns in the 
air with a purple flame, yielding carbon dioxide and nitrogen. 

Water dissolves four and one-half times its volume of cyan- 
ogen. When this solution is left to itself it deposits brown 
flakes. It then contains in solution urea, ammonium carbonate, 
ammonium cyanide, and ammonium oxalate. 



C^N^ 

Cyanogen. 


+ 


4cW0 


= (NH*)2C^0* 

Ammonium oxalate. 


Q2^2 


+ 


WO 


= HCN + ^-2;"N 


Cyanogen. 






Hydrocyanic acid. Cyanic acid. 




+ 


WO 


= CO' + NH^ 


Cyanic acid 






Ammonia. 



The ammonia formed by the latter reaction combines with 



HYDROCYANIC ACID. 465 

the cyanic acid to form ammonium cyanate, which becomes 

converted into urea, as will be seen shortly. 

It is a curious fact that in the presence of a small quantity 
of aldehyde, the decomposition of an aqueous solution of 
cyanogen yields, almost entirely, but one product, — oxamide. 

CW + 2H^0 = ^'^'<^W 

Oxamide. 

If a fragment of potassium be heated in cyanogen gas, a 
brilliant flash of light takes place ; in combining with cyanogen 
potassium becomes incandescent. Potassium cyanide is formed. 
(CN)2 + K^ = 2KCN 

In this reaction, cyanogen combines directly with a metal. 
It acts like an element, such as chlorine, 

Paracyanogen, which has been mentioned before, is a poly- 
meride of cyanogen. When it is quickly heated to redness, it 
is entirely transformed into cyanogen gas. 

HYDEOCYANIC ACID. 

(PRUSSIC ACID.) 
HON = HCy 

Preparation. — G-ay-Lussac prepared hydrocyanic acid by 
heating mercury cyanide with hydrochloric acid. 

An easier process consists in decomposing prussiate of potash 
(potassium ferrocyanide) with sulphuric acid. 8 parts of the 
salt in fine powder are heated in a retort with 9 parts of sul- 
phuric acid, previously diluted with 14 parts of water. 

The neck of the retort is inclined upwards, so that the aque- 
ous vapors are condensed and run back into the retort, while 
the vapor of prussic acid, which is very volatile, is dried by 
passage through a tube containing calcium chloride, and con- 
densed in a receiver placed in a freezing mixture of ice and 
salt. 

Properties. — This acid is a colorless, limpid, and very vol- 
atile liquid, having a penetrating odor resembling that of bitter 
almonds. Its density at 7° is 0.7058. It boils at 26.5°, and 
solidifies to a crystalline mass at — 15°. 

It scarcely reddens blue litmus-paper. On contact with an 
incandescent body, it takes fire and burns with a pale violet 
flame. 



466 ELEMENTS OF MODERN CHEMISTRY. 

It does not keep long in the pure state. It becomes brown, 
and is finally converted into a solid, brown mass. 

It dissolves in water in all proportions. A solution contain- 
ing 2 per cent, is used in medicine. 

When hydrocyanic acid is mixed with its own volume of 
concentrated hydrochloric acid, the mixture gets hot and soon 
deposits abundant crystals of ammonium chloride. The solu- 
tion contains formic acid. 

HCN + 2W0 = CWO' + NH^ 

Hydrocyanic acid. Formic acid. 

In reactions with the hydracids, hydrocyanic acid can function 
like a compound ammonia, N(CH)"' (formonitrile). It unites 
with elevation of temperature with hydrochloric, hydrobromic, 
and hydriodic acids to form compounds, such as N(CH)"'. 
HCl and N(CH)"MII, that may be compared to the ammo- 
nium salts. In these crystalline compounds, the anhydrous 
bases can displace the hydrocyanic acid, as they displace am- 
monia in the ammoniacal salts ; thus, 

N(CH)HC1 -f NH^ = NmCl + HCN 

Cupric oxide displaces hydrocyanic acid in the same manner 
in the hydrobromide of formonitrile. 

The oxidized organic acids unite only with difficulty with 
hydrocyanic acid, and at an elevated temperature (Arm. 
Gautier). 

Hydrocyanic acid is one of the most rapid and most danger- 
ous of poisons. A single drop placed upon the eye of a rabbit 
is sufficient to kill the animal in a few instants, and after vio- 
lent convulsions. 

Hydrocyanic acid may be detected by the following tests : 

1. It gives a white precipitate of silver cyanide with silver 
nitrate, and this precipitate does not darken on exposure to 
light. When properly dried and heated, silver cyanide disen- 
gages cyanogen. 

2. If a drop of hydrocyanic acid be added to a mixed solu- 
tion of ferrous and ferric sulphates, and an excess of potassium 
hydrate be added, a thick, dark-colored precipitate is formed. 
If this be treated with an excess of hydrochloric acid, the fer- 
rous and ferric oxides precipitated will be dissolved, and Prus- 
sian blue will remain, strongly coloring the liquid. 

3. If a drop of hydrocyanic acid be mixed with a drop of 
ammonium sulphide, and then evaporated to dryness, ammonium 



METALLIC CYANIDES. 467 

sulphocyanate is formed, and a blood-red color is produced when 
the spot is touched with a drop of ferric chloride slightly 
acidulated with hydrochloric acid. 

METALLIC CYANIDES. 

We will only consider the two more important metallic cya- 
nides, those of potassium and mercury. 

Potassium Cyanide, KCy = KCN.— This compound is 
prepared by heating well-dried potassium ferrocyanide to red- 
ness in stoneware retorts. After cooling, the black mass is 
exhausted with alcohol; this solvent leaves a black deposit, 
consisting of charcoal and iron, and the solution evaporated in 
vacuo deposits the potassium cyanide as a white, crystalline 
mass. 

This body crystallizes in cubes. It has a caustic taste and 
an after-taste of bitter almonds. It is very poisonous. It is 
quite soluble in water, only sparingly soluble in absolute alco- 
hol. When the aqueous solution is boiled, it disengages 
ammonia, and is converted into potassium formate. This 
reaction takes place slowly in the cold, and is analogous to 
that which has before been described. 

When potassium cyanide is heated with sulphur, it is con- 
verted into potassium sulphocyanate. Iodine dissolves abun- 
dantly in a solution of potassium cyanide ; potassium iodide 
is formed, and cyanogen iodide is deposited in crystals. 

Solution of potassium cyanide dissolves the cyanides of 
many metals, such as zinc, silver, and gold, forming soluble 
double cyanides. This property is utilized in the extraction 
of gold from its ores. 

Mercury Cyanide, HgCy^ = Hg(CN)^ — This compound 
is prepared by dissolving finely-powdered mercuric oxide in an 
aqueous solution of hydrocyanic acid until the odor of the lat- 
ter has entirely disappeared, being careful to avoid an excess 
of the oxide. After concentration and cooling, colorless, anhy- 
drous prisms are obtained, which are unaltered by air and light. 
This is mercury cyanide. It is very poisonous. 

It possesses a nauseous metallic taste, and dissolves in 8 
parts of cold water. 

It is decomposed by heat into mercury and cyanogen ; para- 
cyanogen is formed at the same time. The solution of mer- 
cury cyanide dissolves mercuric oxide, and forms with it a 



468 ELEMENTS OF MODERN CHEMISTRY. 

compound more soluble tlian the cyanide, crystallizing in 
colorless scales. 

FEREOCYANIDES. 

By this name are designated compounds containing cyanogen 
and iron intimately combined together and forming a complex 
radical capable of passing from one compound to another by 
double decomposition. This radical, which is called ferrocy- 
anogen^ contains one atom of diatomic iron combined with six 
cyanogen groups, CN. As each of the latter represents one 
atomicity, it is evident that the group (Cy^^Fey"", in which 
but two atomicities are saturated between the Fe and 2Cy, 
must be tetratomic. Hence ferrocyanogen can combine with 
four atoms of a monatomic metal such as potassium. The im- 
portant compound known as potassium ferrocyanide, or yellow 
prussiate of potash, has such a composition. 

Potassium Ferrocyanide, K'Cy^Fe + 3H'0.— This salt is 
obtained by calcining animal matters, such as blood, horn, the 
debris of skin, leather, etc., in closed iron vessels with potassium 
carbonate. The sintered mass, which contains potassium cy- 
anide, is exhausted with boiling water, and ferrous sulphate is 
added to the solution, which is then evaporated to crystalliza- 
tion ; or the solution is boiled with metallic iron, which dissolves 
with evolution of hydrogen. The iron may also be added to 
the mixture of animal matter and potassium carbonate before 
calcination ; after cooling, the mass is pulverized and exhausted 
with boiling water. The solution contains ferrocyanide. 

When sufficiently concentrated, it deposits the salt in yellow 
crystals, which are derived from a square octahedron. They 
are unaltered by the air, but lose 12.8 per cent, of water at 
100°. The anhydrous salt is white. 

Potassium ferrocyanide dissolves in 2 parts of boiling, and 
in 4 parts of cold water. It is insoluble in alcohol. When 
heated with bodies rich in oxygen, such as manganese dioxide, 
it is converted into potassium cyanate, the iron itself being 
oxidized to peroxide. It is not poisonous. 

When fused with sulphur, it is converted into potassium 
sulphocyanate. 

When heated with concentrated sulphuric acid, it yields pure 
carbon monoxide, and a residue consisting of sulphates of iron, 
potassium, and ammonium. 



POTASSIUM rERRICYANIDE. 469 

Potassium ferrocyanide precipitates many metallic solutions. 
Tlie following are some of these precipitates : 

Zinc ferrocyanide Zn^Cy^Pe, white. 

Copper ferrocyanide Cu^Cy^Fe, mahogany color. 

Lead ferrocyanide Pb^Cy^Pe, white. 

Silver ferrocyanide Ag^Cy^Fe, white. 

Potassium ferrocyanide forms a bluish-white precipitate with 
ferrous salts. This precipitate contains : 

It is identical with the bluish-white deposit which is formed when 
potassium ferrocyanide is heated with dilute sulphuric acid. 

Prussian Blue, (Fe')\Cy^Fe)l— This is the dark-blue pre- 
cipitate obtained when a solution of potassium ferrocyanide is 
poured into a ferric salt. 

4FeCP -\- SK^Cy^Fe = 12KC1 + Fe^Cy^Fe^ 

Ferric chloride. Potassium ferrocyanide. Ferric ferrocyanide. 

(Prussian blue.) 

When calcined in contact with the air, it leaves a residue 
of peroxide of iron. It is insoluble in water, alcohol, and in 
the weaker acids. Oxalic acid dissolves it, and the solution is 
employed as a blue ink. 

POTASSIUM FERRICYANIDE. 

(red prussiate of potash.) 
KsCy^Fe 
This beautiful salt, discovered by Leopold Grmelin, is formed 
when a current of chlorine is passed into a solution of potassium 
ferrocyanide. Potassium chloride and potassium ferricyanide 
are formed, and the latter gives to the liquid a deep green-brown 
color. On evaporation it deposits the new salt, which is puri- 
fied by a second crystallization. Potassium chloride remains 
in the mother-liquor. 

2KXCy«Fe) + CP = 2KC1 -f 2K^Cy«Fe 

Potassium ferrocyanide. Potassium ferricyanide. 

Potassium ferricyanide forms magnificent monoclinic prisms 
of a ruby-red color. These crystals are anhydrous. 

It is believed that this salt contains a triad radical, Cy^Fe, 
which is called fefricyanogen. 

Potassium ferricyanide dissolves in 3.8 parts of cold water, 
and in a less quantity of boiling water. The solution has a 
dark yellow-brown color. It does not precipitate the ferric 

40 



4*70 ELEMENTS OF MODERN CHEMISTRY. 

salts. In solutions of tlie ferrous salts it gives a blue pre- 
cipitate analogous to Prussian blue, and wbicb is called Turn- 
hulTs hlue. 
2K^C/Fe + 3FeS0* = SK^SO* + Fe^Cy^Fey 

Potassium Ferrous sulphate. Potassium Ferrous ferricyanide. 

ferricyanide. sulphate. (Turnbull's blue.) 

In alkaline solution potassium ferricyanide acts as an ener- 
getic oxydizing agent, tbus : 

2K^Cy«Fe + 2K0H = 2K*Cy«Fe + H^O -f 

NITROFEREOCYANIDES. 

These salts, which were discovered by Playfair, are formed 
by the action of nitric acid upon certain alkaline ferrocyanides. 
The best known is sodium nitroferrocyanide, or, as it is ordi- 
narily called, sodium nitroprusside. 

It is prepared by oxidizing potassium ferrocyanide with dilute 
nitric acid. After filtration and evaporation, crystals of potas- 
sium nitrate and a deposit of oxamide are obtained. The 
mother-liquor is saturated with sodium carbonate, and on 
evaporation yields sodium nitroprusside, which may be purified 
by recrystallization. 

Sodium nitroferrocyanide crystallizes in large right rhombic 
prisms of a ruby-red color. Its composition is represented by 
the formula Na'Cy^(NO)Fe -|- 2H'0. Its aqueous solution 
has a red-brown color, and gives a very intense but evanescent 
purple color with solutions of the alkaline sulphides. 

CHLORIDES OF CYANOaEN. 

There are two chlorides of cyanogen known, a chloride, 
CyCl, which is liquid below 15.5°, and a solid chloride, Cy^CP. 
These two chlorides present a curious instance of polymerism. 

Liquid Cyanogen Chloride, CyCl = CNCl.— This com- 
pound is prepared by passing chlorine gas over mercury cy- 
anide, or better, into an aqueous solution of hydrocyanic acid, 
which is maintained at 0°. Hydrochloric acid and cyanogen 
chloride are formed. 

HCN + CP = CNCl + HCl 

When the solution is saturated with chlorine, it is gently 
heated, and the cyanogen chloride which is disengaged is 



AMIDO DERIVATIVES OP CYANOGEN. 471 

passed through a tube containing calcium chloride, and con- 
densed in a well-cooled receiver. 

When properly purified, cyanogen chloride is a colorless 
liquid, having a penetrating odor, which is very irritating to 
the eyes. It boils at 15.5° and solidifies at about 5°. When 
pure, it can be preserved without alteration, but if it contain a 
trace of chlorine, it soon becomes converted into the solid 
chloride. 

Solid Cyanogen Chloride, Cy^CP = C^N^CP.— This body 
results from the polymeric transformation which the liquid 
chloride undergoes spontaneously under certain circumstances. 
It can also be obtained by exposing hydrocyanic acid to the 
action of chlorine in direct sunlight. 

It crystallizes in brilliant, yellow needles or plates. It melts 
at 140° and boils at 190°. It has a peculiar, irritating odor. 
Boiling water immediately decomposes it into hydrochloric and 
cyanuric acids. 

CWCP + SH^O = ^^^sJN^ + 3HC1 

Cyanogen chloride. Cj'anuric acid. 

Cyanogen Bromide and Iodide. — The bromide and iodide 
of cyanogen correspond in constitution to the liquid chloride. 
They are obtained by the action of bromine or iodine upon 
mercury cyanide. These elements decompose mercury cyanide 
with formation of bromide or iodide of mercury, the excess 
of bromine or iodine combining with the cyanogen to form 
cyanogen bromide or iodide. 

Gyajniogen bromide^ CNBr, is solid and crystallizes in bril- 
liant cubes. 

Cyanogen iodide, CNI, sublimes spontaneously in beautiful 
colorless needles when a mixture of iodine and mercury cya- 
nide is placed in the bottom of a flask, mercuric iodide being 
formed. Cyanogen iodide has a penetrating odor ; it is very 
volatile, and, like the chloride and bromide, is very poisonous. 

AMIDO DERIVATIVES OF CYANOGEN. 

Cyanamide, CN^H^ = ^^NW — ^^^^ compound is formed 

by the action of cyanogen chloride or bromide on an ethereal 
solution of ammonia. It is also obtained by the action of mer- 
curic oxide or silver oxide upon sulpho-urea (page 483). 



472 ELEMENTS OF MODERN CHEMISTRY. 

CS<Nff + HgO = HgS + ffO + C<™ 

Sulpho-urea, Cyanamide. 

It forms crystals fusible at 40°, soluble in water, alcohol, 
and ether. Ammoniacal silver nitrate precipitates from its 
solution a yellow silver compound containing CN^Ag^. By 
the action of acids it combines with the elements of water, 
forming urea (page 478). Hydrogen sulphide reconverts it 
into sulpho-urea. 

^<NU + H'S = CS<Nff 
Melamine, C^N^H^ — When cyanamide is heated to 150°, it 
becomes polymerized, and converted into tricyanuramide. This 
substance is known as melamine. It crystallizes in brilliant 
right-rhombic octahedra, soluble in hot water, insoluble in 
alcohol and ether. It unites with acids, forming salts. When 
heated with dilute alkalies or with acids, it is converted suc- 
cessively by the action of one, two, or three molecules of 
water, and elimination of one, two, or three molecules of 
ammonia, into ammeline, ammelide, and cyanuric acid. 

/NH^ /OH /OH /OH 

C^N^NH^ C^N^NH^ C=^N^^OH OW^-OH 
^NH^ ^NH^ ^NH^ ^OH 

Melamine. Ammeline. Ammelide. Cyanuric acid. 

Cyanuric acid, which is formed according to the following 
equation, will be described farther on. 

CW(NH2)^ + SH^O == C^N^Ony + 3Nff 

GUANIDINE. 
CH5N3 

This body is related to the amides of cyanogen. It was 
first obtained by the oxidation of guanine, derived from guano ; 
hence its name. Since then it has been formed synthetically 
by the following reactions. 

1. When an alcoholic solution of either cyanogen iodide or 
cyanamide is heated to 100° with ammonium chloride: 

C<^g + NH^Cl = NH=C<^^'hC1 

Cyanamide. Hydrochloride of guanidine. 

If cyanogen iodide be employed, cyanamide is first formed. 



CARBONYL COMPOUNDS. 473 

2. By the action of carbonyl chloride on ammonia (G. Bou- 
chardat). 

3. By the action of ammonia on either ethyl orthocarbo- 
nate or chloropicrin (page 491). 

C(OC^tP)* -j- 3NH3 = QWW + 4C^H^0H 

Ethyl orthocarbonate. Guanidiae. Alcohol. 

4. The method generally employed for the preparation of 
guanidine consists in heating for a long time ammonium 
sulphocyanate (page 482) to a temperature of 180° or 190°. 
Sulpho-urea is formed, and decomposed into hydrogen sulphide 
and guanidine sulphocyanate. 

2CSN2H* = H^S + CN^H^CNSH 

Sulpho-urea. Guanidine sulphocyanate. 

Properties, — Guanidine forms deliquescent crystals, very 
soluble in water and alcohol. It has a strong alkaline reaction, 
and absorbs carbonic acid gas from the air. With acids it 
forms crystallizable salts. The nitrate, CN^H^.HNO^, precipi- 
tates in plates when nitric acid is added to an aqueous solution 
of guanidine. The carbonate (CN^H^)MI^CO^ crystallizes in 
quadratic prisms the solution of which has an alkaline reaction. 

CARBONYL COMPOUNDS. 

Carbon monoxide plays the part of a diatomic radical. It is 
capable of uniting with one atom of oxygen to form carbonic acid 
gas, or with two atoms of chlorine to form carbonyl chloride. 

It can also unite with two residues, NH^, which are mon- 
atomic since they represent ammonia less one atom of hydro- 
gen ; lastly, it may unite with NH, which is diatomic since it 
represents ammonia minus two atoms of hydrogen. The com- 
pounds thus formed have the following constitutions ": 
CO.O carbon dioxide. 

CI 
CO<^^j carbonyl chloride. 

CO<^g urea. 
CO(NH)" isocyanie acid. 
The last two compounds can be considered as derived from 
the ammonia type. 

Isocyanie acid is derived from one molecule of ammonia by 
the substitution of the diatomic radical CO, which is called 
carbonyl^ for two atoms of hydrogen. 

40* 



474 ELEMENTS OF MODERN CHEMISTRY. 

H -^ 1 H isocyanic aoid. 

Urea is derived from two molecules of ammonia by the sub- 
stitution of the radical carbonjl for two atoms of hydrogen. 
cm rco" 

N2 J H2 W\ H2 urea. 

( H2 Im 

Urea is then carhonyl diamide ; or more simply, carbamide. 

ISOCYANIC ACID. 
CONH 

Liebig and Wohler obtained this acid by the dry distillation 
of cyanuric acid. One molecule of the latter, which is poly- 
meric with isocyanic acid, then breaks up into three molecules 
of the latter body. 

C^OWH^ ^ 3C0NH 

Cyanuric acid. Isocyanic acid. 

The latter acid condenses at a few degrees below 0° to a color- 
less liquid having a strong and irritating odor. It is very 
unstable. As soon as it is removed from the freezing mixture 
in which it is condensed, and its temperature rises to a few 
degrees above 0°, it produces a crackling noise and little ex- 
plosions, and is converted by a molecular transformation into 
an amorphous white mass called cyamelide. The latter body 
is also formed at the same time as isocyanic acid by the dry 
distillation of cyanuric acid. 

Potassium Isocyanate, CONK. — This salt is prepared by 
heating to dull redness in a flat sheet-iron dish an intimate 
mixture of 2 parts of potassium ferrocyanide and 1 part of 
manganese dioxide, both in fine powder and perfectly dry. 
The mixture must be continually stirred ; it blackens and 
enters into semi-fusion ; after cooling, it is reduced to powder 
and exhausted with hot alcohol of 80 per cent. On cooling, 
the filtered alcoholic solution deposits potassium isocyanate in 
laminated, transparent crystals which are anhydrous. This salt 
is very soluble in water, and but slightly soluble in cold concen- 
trated alcohol. If hydrochloric acid be added to an aqueous 
solution of potassium isocyanate, carbonic acid gas is disengaged 
with brisk effervescence. The liquid contains ammonium 
chloride. 

CONH -f H^O -= CO^ + NH» 



CYANIC ACID. 475 

Potassium Cyanate. — There is a compound isomeric with 
potassium isocyanate ; it is formed by the action of cyanogen 
chloride upon potassium hydroxide (Bannow). 

CN.Cl + 2K0H =. KCl + IPO + KCNO 

Cyanogen chloride. Potassium cyanate. 

The hydrate corresponding to this potassium salt would be 
the true cyanic acid, of which the ethers were discovered by 
Cloez. The compound formerly known by the name cyanic acid 
does not merit that name. It is not a compound of cyanogen, 
but a combination of oxide of carbon ; it is carhimide. It is 
the isocyanic acid vn'hioh we have just described. The follow- 
ing formulas will explain this curious isomerism. 

H-O-CeN H-N=C=0 

Cyanic acid. Isocyanic acid. 

K-O-CEN K-N=C=0 

Potassium cyanate (Bannow). Potassium isocyanate (ordinary cyanate). 

C^H^-O-CeN C^H5-N=C=0 

Etliyl cyanate Ethyl isocyanate. 

(Oloez). (Cyanic ether of Wurtz.) 

Ammonium Isocyanate. — This is formed when vapor of 
isocyanic acid is passed into a flask containing ammonia gas. 
It is a solid, white mass, very soluble in water. When its 
aqueous solution is treated with hydrochloric acid, it disengages 
carbon dioxide like the solution of potassium isocyanate. If 
its aqueous solution be boiled, or even left to itself for several 
days, ammonium isocyanate becomes transformed into urea. 

(NH^)CON = CO<^g, 

Ammonium isocyanate. Urea, 

CYANURIC ACID. 

C3N3H303 = C3N3(OH)3 

Cyanuric acid is formed by the action of water upon the 
solid cyanogen chloride, by the action of heat on urea, or by 
that of dilute acetic acid on a solution of potassium isocyanate ; 
in the last case, potassium acid cyanurate, C^N^H^KO^, is pre- 
cipated after a time, and liberates cyanuric acid when treated 
with hydrochloric acid. 

Preparation.- — Small quantities of urea are heated in an 
oil-bath until ammonia is no longer disengaged. The gray 
mass remaining is pulverized and dissolved in dilute potassium 



476 ELEMENTS OF MODERN CHEMISTRY. 

hydrate : when the filtered solution is treated with hydrochloric 
acid, cyanuric acid is obtained as a white precipitate. 

Another process consists in decomposing urea by a stream 
of dry chlorine at a temperature of 130° or 140°. Nitrogen 
and hydrochloric acid are disengaged, and there remains a 
mixture of cyanuric acid and ammonium chloride which may 
be separated by cold water. The residue consisting of cyanuric 
acid is exhausted with boiling water, which, on cooling, deposits 
the acid in crystals. 

SCON^H* + CP = CWH^O^ + 2NH*C1 + HCl + N 

Urea. Cyanuric acid. 

Properties. — Cyanuric acid occurs in small white crystals, 
soluble in forty parts of cold water, very soluble in boiling 
water and in alcohol. It separates from its boiling aqueous 
solution in orthorhombic prisms containing two molecules of 
water of crystallization. When strongly heated it yields 
isocyanic acid. Phosphorus pentachloride converts it into solid 
cyanogen chloride. 

C^NXOH)^ + 3PC15 = 3P0CP + C^N^CP + 3HC1 

By this reaction, and by its formation from cyanogen chlo- 
ride, cyanuric acid is related to the cyanogen compounds, and 
the relation is expressed by the formula C^N^(OH)^. 

When it is boiled with strong acids, cyanuric acid is decom- 
posed into carbon dioxide and ammonia. 

CWH^O^ _l_ 3H20 = 3C0^ + 3NH^ 

This reaction recalls the analogous decomposition of isocyanic 
acid (page 474), and relates cyanuric acid to carbimide. From 
this point of view, cyanuric acid would be tricarbimide, — that 
is, three molecules of carbon monoxide (carbonyl) united by the 
intervention of three imidogen groups (NH). 

(CO.NH)' = CO<^g-^g>NH 

It is, then, possible that there may be two isomeric modifica- 
tions of cyanuric acid. There are certainly two isomerides of 
its ethers : the trimethylic ether of the true cyanuric acid, 
C^N^(OCH^)^, is formed by the action of cyanogen chloride on 
sodium methylate ; and, on the other hand, there are ethers 
of tricarbimide or isocyanuric acid, which will be described 
farther on. 



CARBAMIC ACID — UREA. 477 



CARBAMIC ACID. 

OTT 

This acid is not known in the free state. Its ammonium 
salt is commonly known as anhydrous ammonium carbonate ; its 
ether, urethane, or ethyl carbamate, is described on page 515. 

Ammonium carbamate. Urethane. 

When two volumes of ammonia gas and one volume of 
carbon dioxide are mixed over the mercury trough, a white 
mass is obtained ; this exists in the ammonium carbonate of 
commerce, and constitutes ammonium carbamate. At 60°, it is 
dissociated and resolved into its constituent gases, one molecule 
of ammonium carbamate yielding four volumes of ammonia 
and two volumes of carbon dioxide. Water converts it into 
ammonium carbonate. 

CO<ONp ^ ^.o = CO<S 

Ammonium carbamate. Ammonium carbonate. 

Ammonium carbamate is intermediate between urea and 
ammonium carbonate. 

'""<ONH* ^"<Nff ^"<Nff 

Ammonium carbonate. Ammonium carbamate. Urea. 

UREA OR CARBAMIDE. 

CO(NH2j2 

This body, discovered by Rouelle in 1773, is the most 
abundant of the solid constituents of urine. Wohler was the 
first to obtain urea artificially by heating an aqueous solution 
of ammonium isocyanate. 

CONNH* = CO(NH^)^ 

This discovery was the first instance of the synthesis of an 
organic body. 

Urea is also formed by many other reactions. 

1. By the action of carbonyl chloride upon ammonia 
(Natanson). 

C0<^} + 2NH^ =: CO<^g', + 2HC1 



478 ELEMENTS OP MODERN CHEMISTRY. 

2. By the action of ammonia on ethyl carbonate. 

Ethyl carbonate. Urea. Alcohol, 

3. When ammonium carbamate is heated to 130° or 140° 
under pressure in sealed tubes. 

Ammouium carbamate. 

These reactions show clearly that urea is the amide corre- 
sponding to carbonic acid, — that is, carbamide. Indeed, it 
represents neutral ammonium carbonate, less two molecules 
of water. 

4. Urea is formed by the action of small quantities of acids 
on cyanamide. 

Cyanamide. Urea. 

5. When oxamide is heated with mercuric oxide (Williamson), 

C'0'<Nff + = CO' + CO<^g, 

Oxamide. 

Preparation. — 1. Urea may be obtained from urine by the 
following process. The urine is evaporated to a syrupy consist- 
ence on a water-bath. It is allowed to cool, and an excess of 
cold nitric acid is added ; a mass of crystals are formed, which 
ordinarily have a brown color. They are drained, washed with 
a little ice-water, redissolved in hot water, and animal charcoal 
which has been washed with hydrochloric acid is added. The 
whole is heated on a water-bath for a few minutes and then 
filtered. Colorless crystals of urea nitrate are obtained on 
cooling. 

They are dissolved in water, and barium carbonate is 
added until all eiFervescence ceases. Carbon dioxide is dis- 
engaged, and barium nitrate is formed, while the urea is set 
free. The filtered liquor is evaporated to dryness on the 
water-bath, and the residue exhausted with absolute alcohol, 
which dissolves the urea, while the barium nitrate remains. 
The alcoholic solution is concentrated, and urea crystallizes 
out. 



UREA. 479 

2. Potassium isocyanate is prepared by heating 28 parts of 
well-dried potassium ferrocyanide with 14 parts of manganese 
dioxide, as has been already indicated. The cooled mass is 
coarsely powdered, and exhausted with cold water, which dis- 
solves the potassium isocyanate. 20 parts of ammonium sul- 
phate are added to the filtered liquid, which is then evaporated 
to dryness on a water-bath. The residue is exhausted with 
boiling alcohol, which dissolves the urea and leaves potassium 
sulphate. 

In this operation the potassium isocyanate and ammonium 
sulphate undergo double decomposition, with formation of 
potassium sulphate, and ammonium isocyanate which is trans- 
formed into urea. 

Properties. — Urea separates from its aqueous solution in 
long, flattened, and striated prisms. It sometimes deposits 
from its alcoholic solution in square prisms. 

The crystals are colorless and possess a cooling taste. They 
dissolve in their own weight of water at 15°, and in 5 parts 
of cold alcohol of specific gravity 0.816. They are but slightly 
soluble in ether. 

If a solution of urea be added to a concentrated solution of 
chloride of lime, there is an abundant disengagement of gas, 
which is a mixture of nitrogen and carbon dioxide. The urea 
is entirely destroyed. 

CH*N^O + H^O + 3CP = QO' + N^ + 6HC1 

This reaction serves for the estimation of urea in urine. 
The volume of nitrogen disengaged when a given volume of 
the urine is treated with sodium hypobromite, is measured, and 
the corresponding quantity of urea is calculated. 

An aqueous solution of chlorine produces the same decom- 
position. 

Nitrous anhydride instantly destroys urea, with formation of 
water, carbon dioxide, and nitrogen. 

CHWO -f N^O^ = CO^ -j- 2H^0 + 2W 

When an aqueous solution of urea is heated to 140° in a 
sealed tube, it absorbs the elements of water, and is converted 
into ammonia and carbon dioxide. 

This conversion of urea into carbonate of ammonia takes 



480 ELEMENTS OF MODERN CHEMISTRY. 

place spontaneously in stale urine, under the influence of a 
peculiar ferment (Van Tieghem, Musculus). 

Urea fuses at 132°. When it is rapidly heated to a higher 
temperature, it disengages ammonia and leaves a white residue, 
which consists principally of cyanuric acid (page 475). There 
are also formed ammelide and biuret (page 481). 

When urea is heated with ethyl chlorocarbonate (page 516), 
ethyl allophanate is formed. 

Ethyl Ethyl allophanate. 

chlorocarbouate. 

Liebig, who discovered this compound, obtained it by passing 
vapor of isocyanic acid into absolute alcohol. Ethyl allophanate 
crystallizes in brilliant prisms, soluble in alcohol and in boiling 
water, and fusible at 190°-191°. It is a substituted urea, one 
atom of hydrogen, in the latter being replaced by the group 

co.oc^m 

Compounds of TTrea with Acids. — If nitric acid be added 
to a concentrated solution of urea, the liquid becomes a white, 
crystalline, laminated mass, composed of crystals of urea nitrate, 
CH^N^O.HNO^, which are only slightly soluble in nitric 
acid. These crystals are soluble in water and alcohol. They 
strongly redden litmus solution. They decompose at 140°, 
disengaging a large quantity of gas. 

The hydrochloride of urea, CH^N^O.HCl, and the oxalate, 
(GH'N207C'H20^ are known. The latter salt precipitates in 
small, colorless, granular crystals when a concentrated solution 
of oxalic acid is added to a concentrated solution of urea. 

Compounds of Urea with Oxides and with Salts. — There 
are several compounds of urea with mercuric oxide. They 
are formed either by the direct action of mercuric oxide upon 
urea, which dissolves that oxide, or by the reaction of mercuric 
chloride or nitrate upon urea, which is precipitated by both of 
these salts. A solution of urea converts recently-precipitated 
silver oxide into a gray powder, which is a compound of urea 
and oxide of silver. Among the compounds of urea with the 
various salts, that which it forms with sodium chloride is the 
most important. It crystallizes in colorless, oblique rhombic 
prisms, containing CH^N'^O.NaCl + H^O. 

Among the bodies closely related to urea there is an in- 
teresting isomeride, {surety which is formed by the action 



COMPOUND UREAS — BIURET. 481 



of hydrocyanic acid on hydroxylamine ; also hydroxyl urea, 
on hydroxylamine. 



NTT OH 
C0<ATTT2 ) which is formed by the action of isocyanic acid 



COMPOUND UREAS. 

The compounds which are derived from urea by the substi- 
tution of the various alkyl groups for hydrogen are called 
compound ureas. They are obtained either by the action of 
cyanic acid upon the compound ammonias, or by treating the 
cyanic ethers with ammonia or with the compound ammonias 
(Ad. Wurtz). 



CONH + 




- co^-^^^^'^') 




Cyanic acid. 


Ethylamine. 


Etliylurea. 




CON(C^H0 


-f NH^ = 


- co^^^(^'^') 




Ethyl cyanate. 




Ethylurea. 




The following is the nomenclature and composition of 


some 



of the principal compound ureas : 

CH*N20 urea. 
CH3(CH3)N20 methylurea. 
CH3(C2H5)N20 ethylurea. 
CH2(C2H5)2N20 diethylurea. 
CH(C2H5)3N20 triethylurea. 
CH3(C5Hii)N20 amylurea. 
CH3(C6H5)N20 phenylurea. 
CH2(C6H5)2N20 diphenylurea. 

BIURET. 

C2H5N302 

Biuret is the amide of allophanic acid, the ethyl compound 
of which is described on the preceding page, and is formed 
when allophanic ether is heated to 100° with aqueous ammonia. 

Ettiyl allophanate. Biuret. Alcohol. 

It is also formed by the action of heat on urea. 

2C0N^H* = C^OWH^ + NH^ 

V # 41 



482 ELEMENTS OF MODERN CHEMISTRY. 

Biuret crystallizes in delicate needles, or in little masses, 
containing one molecule of water of crystallization. In the 
presence of potassium hydroxide its aqueous solution dissolves 
cupric oxide with the production of a violet-red color. 



Closely related to the compounds of carbon monoxide are 
the following bodies, in which the radical sulphocarbonyl, CS, 
replaces the analogous radical carbonyl CO. 



POTASSIUM THIOCYANATE (SULPHOCYANATE). 

KCSN 

This salt, which was formerly called potassium sulpho- 
cyanide, corresponds to the isocyanate, in which the oxygen 
is replaced by sulphur. 

It is prepared by heating a mixture of two parts of potas- 
sium ferrocyanide and one part of sublimed sulphur to redness 
in a covered crucible. After cooling, the mass is dissolved in 
water, the solution filtered, and potassium carbonate added 
to the liquor as long as a precipitate of ferrous carbonate is 
formed. The solution is again filtered, evaporated to dry- 
ness, the residue exhausted with alcohol, and the alcoholic 
solution allowed to evaporate spontaneously. 

Potassium thiocyanate crystallizes in long striated prisms 
resembling potassium nitrate, or in needles terminated by 
four-faced points. It is deliquescent and very soluble in 
water and alcohol. 

Solution of potassium thiocyanate produces an intense 
blood- red color with the ferric salts, due to the formation of 
ferric thiocyanate. 

Ammonium Thiocyanate, NH^CSN. — This body corre- 
sponds to ammonium isocyanate. It occurs in the water 
from the purification of coal-gas. When heated to 170°, it 
is converted into sulpho-urea (Reynolds). 

The sulphocyanates present an isomerism exactly like that 
which has been mentioned for the cyanates : there is a series 
of compounds derived from a thiocyanic acid, NeC-SH, and 
another series derived from an isothiocyanic acid, (CS)''NH. 
To the latter series belong the ordinary thiocyanates, examples 
of which have just been described. 



MONATOMIC ALCOHOLS. 483 



SULPHO-UREA, OR SULPHOCARBAMIDB. 

Sulpho-urea, which was discovered by Reynolds, is formed 
by a molecular metamorphosis of ammonium sulphocyanate, as 
urea is formed by the metamorphosis of ammonium isocyanate. 

CS-N'"-N-H* becomes CS<i^g2 

It, is also formed by the direct combination of hydrogen 
sulphide and cyanamide (page 472). 

It crystallizes sometimes in fine, silky needles, sometimes in 
large orthorhombic prisms. It is very soluble in water and 
alcohol, slightly soluble in ether. It has a bitter taste and a 
neutral reaction. It melts at 149°, and if heated with water 
to 140° is reconverted into ammonium sulphocyanate. With 
acids it forms crystallizable salts. When treated with mercuric 
oxide, it yields cyanamide. 



MONOHTDKIC ALCOHOLS AND THEIR 
DERIVATIVES. 

These compounds form part of the great class of alcohols. 
They are neutral hydroxides, derived from hydrocarbons by 
the substitution of the radical hydroxy 1 OH for an atom of 
hydrogen. Among these bodies, the more important are those 
which belong to the same series, as ordinary alcohol, or ethyl 
hydroxide, which has been indicated on page 450. Wood- 
spirit, or methyl hydroxide, is the simplest term of the series. 
While studying its combinations, in 1835, Dumas and Peligot 
were the first to call attention to the function " alcohol." 

METHYL COMPOUNDS. 

In these compounds we assume the existence of a radical, 
CH^, to which the name methyl is given. Wood-spirit is its 
hydroxide; marsh gas, or methane, its hydride. To this 
hydride correspond a chloride, a bromide, and an iodide. 
Chloroform is dichloro-methyl chloride, or trichloromethane. 
Around methyl hydroxide are grouped the salts of methyl, or 
methylic ethers, resulting from the action of the acids upon 



484 ELEMENTS OF MODERN CHEMISTRY. 

that body, and whicli bear tbe same relations to methyl hydrox- 
ide as the potassium salts do to potassium hydroxide. They 
are the compound methyl ethers. The following formulae 
indicate the relations which exist between these bodies : 

Methane, or methyl hydride. Methyl hydroxide. 

PTT3 
CH^Cl CW>^ 

Methyl chloride. Methyl oxide. 

CHOP ^ CW>^ 

Chloroform. Methyl acetate. 

These compounds will be but briefly described. 

METHANE. 

(marsh gas.) 

The inflammable gas which is disengaged from the mud of 
marshes is impure methane. The same gas is frequently 
evolved in the galleries of coal mines, and constitutes the 
fire-damp of miners. It is produced artificially by the action 
of an excess of alkali upon acetic acid (Persoz, Dumas). 

Preparation. — Methane is most conveniently prepared in 
the pure state by strongly heating in a glass flask or retort a 
mixture of 1 part of sodium acetate, 1 part of potassium hy- 
droxide, and 1 1 parts of lime ) the lime is added to prevent 
the action of the potassium hydroxide upon the glass. The 
gas may be collected over water. 

NaC^H^O^ + NaOH = CH* + Na^CO^ 

Sodium acetate. Methane. 

Properties. — Methane is a colorless, odorless gas. Its den- 
sity is 0.559 ; it is but slightly soluble in water, somewhat more 
so in alcohol. It burns in the air with a pale, almost non- 
luminous flame. A mixture of methane and oxygen explodes 
violently on the application of flame or the passage of an 
electric spark. 

If two volumes of methane and four volumes of oxygen be 
introduced into an eudiometer and the spark be passed, a bright 
flash is visible. After the combustion, the mercury rises in the 
tube, and it is found that the volume of gas is reduced to one- 



METHYL HYDROXIDE. 485 

third of the original volume (to 2 volumes); if a solution 
of caustic potash be introduced, the whole of the remaining 
gas will be absorbed. 2 volumes of methane produce in burn- 
ing 2 volumes of carbon dioxide, and require 4 volumes of 
oxygen. This experiment establishes the molecular com- 
position of methane. 

2 volumes of carbon dioxide contain 2 volumes of oxygen 
combined with 1 volume (1 atom) of carbon ; consequently 
one molecule of marsh gas contains one atom of carbon. 

The other 2 volumes of oxygen consumed have combined 
with 4 volumes of hydrogen, contained in 2 volumes of 
methane ; that is, the molecule of methane contains 4 atoms 
(=2 molecules) of hydrogen. 

Hence it follows that a molecule of methane contains 1 
atom of carbon and 4 atoms of hydrogen. 

A mixture of chlorine and methane explodes when exposed 
to direct sunlight. In diffused daylight, the action is less 
violent, especially if an inert gas, such as carbon dioxide, be 
added. In this case, methyl chloride is formed, and in pres- 
ence of an excess of chlorine, methylene chloride, chloroformj 
and jfinally carbon tetrachloride. 

CH* + CP = HCl + CH^Cl methyl chloride. 
CH* + 2CP = 2HC1 + CH^CP methylene chloride. 
CH* + 3CP = 3HC1 + CHCP chloroform. 
CH* + 4CP = 4HC1 + CCP carbon tetrachloride. 

It is seen that in these reactions the chlorine is substituted 
for hydrogen, atom for atom. 

Inversely, when these substitution products are submitted 
to the action of nascent hydrogen, an inverse substitution is 
effected : they are reconverted into methane. This may be 
accomplished by putting the chlorine compounds in contact 
with sodium amalgam and water. The latter is decomposed by 
the sodium, and constitutes a source of hydrogen (Melsens). 

CHCP + 3H2 = 3HC1 + CH* 

METHYL HYDROXIDE, OR METHYL ALCOHOL. 

(wood-spirit.) 
CH*0 = CH3-0H 

The products of the dry distillation of wood contain about 
one per cent, of a spirituous liquid, which was discovered in 

41* 



486 ELEMENTS OF MODERN CHEMISTRY. 

1812 by Taylor, and named wood- spirit. It is separated by 
several distillations and rectifications over lime ; for, being 
more volatile tlian the other products, it passes over first. 

The methyl alcohol of commerce is always impure, and 
cannot be purified by fractional distillation, as it contains a 
considerable proportion of acetone, of which the boiling-point 
(56°) is very near that of niethyl alcohol. The impurities 
may be removed by treating the impure alcohol with cal- 
cium chloride, with which it forms a crystalline compound, 
CaCP -j- 4CH^.0H. The crystals are drained, dried between 
folds of blotting-paper, and distilled with water, when they 
yield dilute methyl alcohol. This is rectified by repeated 
distillation, and finally dehydrated over quick-lime. 

To obtain the alcohol perfectly pure, an ether of methyl 
is prepared and freed from all impurities by either crystal- 
lization or distillation. The ether is then decomposed with 
an alkaline hydroxide, and the methyl alcohol formed is dis- 
tilled ofi" and dehydrated over lime. Thus, methyl oxalate 
is prepared by treating the still impure methyl alcohol with 
oxalic acid, and is purified by crystallization. 

2CH10H -I- eO^ff == (CH^.C^O* + 2H20 

Methyl hydroxide. Oxalic acid. Methyl oxalate. 

The methyl oxalate is boiled with potassium hydroxide, 
and the methyl alcohol which distils is rectified over quick- 
lime. 

(CWy.C'O' + 2K0H = 2CH10H -f C^^O^K^ 

It is a mobile, colorless liquid, having an alcoholic odor. 
It boils at 66.5°. Its density at 0° is 0.8142. 

It is inflammable and burns with an almost colorless flame. 
It is miscible with water, alcohol, and ether in all proportions. 
It dissolves caustic baryta, forming a definite combination. 

Potassium and sodium react energetically upon methyl hy- 
droxide ; the metal dissolves with disengagement of hydrogen 
and formation of an alkaline methylate or methoxide. 

CH'-OH CH'-OK 

Methyl hydroxide. Potassium methylate. 

If methyl alcohol be placed under a bell-jar containing also 
some watch-glasses filled with platinum black, so that the vapor 
of the wood-spirit mixed with air may come in contact with 
the finely-divided metal, it is found that the liquid soon becomes 



CHLORIDE, BROMIDE, AND IODIDE OF METHYL. 487 



strongly acid. By the slow oxidation of the wood-spirit under 
these conditions, formic acid and formaldehyde are produced. 

Cff-OH + 0^ = CHO-OH + H^O 

Methyl hydroxide. Formic acid. 

2CH3-OH + 0' = 2H-CH0 + 2H^0 

Formaldehyde. 



METHYL OXIDE, OK METHYL ETHER. 

(CH3)20 

When methyl alcohol is heated with twice its weight of 
concentrated sulphuric acid, a colorless gas is disengaged, which 
is methyl oxide. 

2CH3.0H = (Cff)^O + WO 

Methyl hydroxide. Methyl oxide. 

This gas is formed by the dehydration of methyl alcohol 
and the linking together of two methyl groups by an atom of 
oxygen. Methyl ether is readily absorbed by water, and is 
even more soluble in alcohol and ether. It liquefies at — 23°. 

CHLORIDE, BROMIDE, AND IODIDE OF METHYL. 

These compounds may be regarded as marsh gas in which 
one atom of hydrogen is replaced by an atom of chlorine, bro- 
mine, or iodine. 

They are formed by the action of hydrochloric, hydrobromic, 
and hydriodic acids upon methyl alcohol. 

Cff.OH + HCl = CH^Cl + ffO 

Hence they are considered as derived from the hydracids by 
the substitution of the group methyl for the atom of hydrogen. 

HCl (CH3)C1 

Hydrochloric acid. Methyl chloride. 

Methyl chloride is a colorless gas, having an agreeable odor. 
When exposed to intense cold, it condenses to a liquid which 
boils at — 22°. When heated for a considerable time with a 
concentrated solution of potassium hydroxide, it is converted 
into methyl alcohol. Liquid methyl chloride is employed in- 
dustrially in the production of cold, and large quantities are 
consumed in the manufacture of dye-stuffs. 

3Iethi/l iodide, CH^I, boils at 43° ; its density at 0° is 2.1992. 



488 ELEMENTS OF MODERN CHEMISTRY. 

It is made by gradually adding iodine to a mixture of methyl 
alcohol and amorphous phosphorus, and distilling. The dis- 
tilled liquid is mixed with water, which precipitates the iodide ; 
the dense liquid is separated, dried with calcium chloride, and 
distilled. 

METHYLENE CHLOEIDE. 

CH^CP 

This compound may be prepared by the action of chlorine 
on methane, or on methyl chloride, or by the reduction of 
chloroform by nascent hydrogen. The latter method is the 
more convenient. An alcoholic solution of chloroform is treated 
with zinc in a flask connected with a condenser, and hydrochlo- 
ric acid is introduced in small portions. Methylene chloride 
and unaltered chloroform distil over, and towards the close of 
the operation the distillation is continued by the aid of heat. 
The distillate is then washed, dried, and submitted to fractional 
distillation. 

Methylene chloride is a mobile liquid, having an odor resem- 
bhng that of chloroform, and boiling at 40°. Its density at 0° 
is 1.36. 

METHYLENE IODIDE, 

CH^P, 

is made by the action of hydriodic acid on chloroform or iodo- 
form in sealed tubes at a temperature of 150°. 

CHOP + 4HI = CH^r H- 3HC1 + P 
It is also formed by the action of sodium ethylate on iodo- 
form. It is a yellow, highly refracting liquid, having a density 
of 3.342 at 5°, and soHdifying at 2°. It boils at 182°, with 
partial decomposition. 

OCH' 
Methylal, or the dimethylic ether of methylene, CH^<^QpTj3, 

is obtained by the action of sulphuric acid and manganese di- 
oxide on methyl alcohol. It is a limpid liquid, boiling at 42°. 
Its reactions are identical with those of formaldehyde (p. 545). 

QQ2JJ5 

Methylene diethylate, CH^<Qp2TT5j the ether intermediary 

between methyl-ethyl oxide (p. 502) and Kay's ether (p. 489), 
may be obtained by the action of sodium ethylate on methylene 
chloride (Greene). 



CHLOROFORM. 489 

CH^CP + 2C^H50Na = 2NaCl -]- CW(OCmy 

It is an ethereal liquid, having a pleasant, penetrating odor. 
Its density at 0° is 0.851, and it boils at 89°. 

Methylene diacetate, CH2<^2jj3Q2, is formed by the action 

at 100° of silver acetate on methylene iodide in presence of 
acetic acid (Boutlerow). It is an aromatic liquid, which when 
heated with lead oxide is decomposed into lead acetate and 
oxymethylene (p. 545). 

3CHXC^H^0^)^ + 3PbO = 3Pb(C^H^O0' + C^H«0^ 

Methylene diacetate. Lead acetate. Trioxymethylene. 

CHLOROFORM. 

CHOP 

This important substance was discovered in 1831 by Soubei- 
ran and Liebig. It is made by distilling either dilute alcohol 
or acetone with bleaching powder (chloride of lime). The 
distilled liquid separates in two layers, of which the lower 
is impure chloroform. It is separated, washed first with water 
and then with a solution of potassium carbonate, and rectified 
over calcium chloride. 

Chloroform is a colorless, very mobile liquid, having an 
agreeable, ethereal odor. Its density at 0° is 1.525, and it 
boils at 60.8°. It does not take fire on contact with flame. 

It is but slightly soluble in water, but dissolves readily in 
alcohol and ether. It dissolves sulphur, phosphorus, fats, 
resins, a great number of the alkaloids, and in general, organic 
matters rich in carbon. 

By the prolonged action of chlorine, it is converted into 
carbon tetrachloride, CCP, a colorless liquid boiling at 77°. 

A boiling alcoholic solution of potassium hydroxide con- 
verts it into formate and chloride. 

CHCP + 4K0H = 2ff + 3KC1 + KCHO^ 

Chloroform. Potassium formate. 

When chloroform is boiled with an alcoholic solution of 
ethylate of sodium, sodium chloride is formed, together with 
an ethereal compound, CH(OC^H°)^, in which 3 oxethyl groups, 
OC^H^, replace the 3 chlorine atoms of chloroform (Kay). 

CHCP + 3NaO.C^H5 = 3NaCl + CH(0C^H^)3 

Chloroform. Sodium ethylate. Kay's ether. 



490 ELEMENTS OP MODERN CHEMISTRY. 

Cliloroform, heated to 180° witli aqueous or alcoholic ammo- 
nia, yields ammonium cyanide and sal-ammoniac. This re- 
action takes place at 100°, in presence of potassium hydroxide. 
CHCP + SNIP = NH*CN + SNH^Cl 

Chloroform acts in a remarkable manner upon the phenols 
in presence of an alkali such as soda or potassa, forming aro- 
matic aldehydes. This reaction, discovered by Reimer, will be 
described farther on (see Phenol). 

When heated with an alcoholic solution of ethylamine in 
presence of potassium hydroxide, chloroform yields ethyl- 
carbylamine (page 509), A similar reaction occurs with other 
bases analogous to ethylamine, such as aniline. This reaction 
characterizes the primary amines (Hofmann). 

Chloroform is much employed in surgery as an anaesthetic. 
The inhalation of its vapor produces insensibility and loss of 
muscular action, and apparently without any danger, provided 
the preparation is free from impurities. 

BROMOFORM. 

CHBrS 

Bromoform may be made by the action of bromine on a solu- 
tion of an alkaline hydroxide in alcohol or acetone. Potas- 
sium or sodium hydroxide is dissolved in its own weight of 
crude methyl alcohol, and to the solution, which is cooled in 
ice-water, bromine is added in Small portions until the liquid 
begins to assume a permanent color. The product of the 
reaction is agitated with water, and the oily liquid which sepa- 
rates is washed, dried, and rectified. 

Bromoform is an oily liquid, having an agreeable odor, re- 
sembling that of chloroform. Its density is 2.'77, and it boils 
at about 150°. Insoluble in water, it dissolves readily in alcohol 
and ether. Its reactions are similar to those of chloroform. 

IODOFORM. 

CHP 

Iodoform is formed by the simultaneous action of iodine and 
an alkaline hydroxide on alcohol and many other organic sub- 
stances. It is prepared by dissolving two parts of crystallized 
sodium carbonate in ten parts of water and one part of alcohol ; 
the solution is heated to 80°, and one part of iodine is added 



NITROFORM — CHLOROPICRIN. 491 

in small portions. Iodoform separates in yellow scales. If 
alcohol and potassium hydroxide be added to the mother liquid 
and chlorine be passed through, an additional quantity of iodo- 
form may be obtained. 

Iodoform crystallizes in brilliant yellow, hexagonal scales, 
which sometimes assume large dimensions. 

It has a peculiar odor, recalling that of saffron. It melts at 
119°, and cannot be distilled, but at 100° its tension of vapor 
is sufficient to allow it to volatilize with the vapor of water. 
Insoluble in water, it dissolves in alcohol and ether. By the 
aid of heat, hydriodic acid converts it into methylene iodide with 
separation of iodine. 

CHP + HI = CH^P -f- P 

This reduction by hydriodic acid is only one example of the 
action of that acid on carbon compounds generally. The extent 
of the reduction depends upon the temperature at which the 
reaction takes place. Iodine is always set free in these cases. 

Owing to its antiseptic properties, iodoform is extensively 
used in surgery. 

NITKOFORM. 

CH(N02)3 

This compound is trinitromethane, — that is, methane, CH*, 
in which three atoms of hydrogen are replaced by three nitryl 
groups, NO^. It is formed in small quantity by the action of 
nitric acid on various organic compounds. It is also formed 
when trinitroacetonitrile (p. 493) is boiled with water. 
C(NO^)^-CN + 2H20 = CH(NO^)lNH^ -f CO^ 

Trinitroacetonitrile. Ammonia compound of nitroform. 

From the ammonia compound formed in this reaction, sul- 
phuric acid separates nitroform as a thick, colorless ail, which 
below 15° solidifies in cubical crystals. 

Nitroform is soluble in water ; when rapidly heated it ex- 
plodes. It plays the part of an energetic acid ; the single atom 
of hydrogen which it contains is strongly basic, by reason of 
its proximity to the three nitryl groups. There is a potassium 
salt C(NO^)^K. 

CHLOEOPICRIN. 
CC13(N02) 

Chloropicrin, which has long been known, represents chloro- 
form in which the hydrogen atom is replaced by the group NOl 



492 ELEMENTS OF MODERN CHEMISTRY. 

It is formed by the action of nitric acid on many chlorine or- 
ganic compounds, such as chloral. On the other hand, it may 
be obtained by the reaction of chlorine or chlorinated lime on 
nitrogenized organic compounds, such as picric acid, mercuric 
fulminate, etc. It is prepared by distilling a milk of chlorinated 
lime with a saturated solution of picric acid. Chloropicrin then 
distils with the vapor of water.. 

It is a colorless liquid, having a very irritating odor and 
exciting tears. Its density is 1.665. It boils at 112°, but ex- 
plodes when heated suddenly. Nascent hydrogen, produced by 
the action of acetic acid and iron, converts it into methylamine. 

CCP(NO^) -f- 6W = CHINH^ -f- 3HC1 + 2H20 

Chloropicrin. Methylamine. 

There is a bromopicrin, CBr^(NO^), prepared by a reaction 
analogous to that which yields chloropicrin, which it resembles 
in its general properties. 

CARBON TETKACHLORIDE. 

CCl* 

Carbon tetrachloride, or tetrachloromethane, is obtained by 
the prolonged action of chlorine on chloroform in direct sun- 
light, or by passing through a red-hot porcelain tube a mixture 
of chlorine and vapor of carbon disulphide. In the latter re- 
action sulphur chloride is also formed, and must be removed by 
agitating the product with a solution of potassium hydroxide. 

Carbon tetrachloride is a colorless liquid, having an agreeable 
odor like that of chloroform. Its density at 0° is 1.629. It 
boils at 77°. When its vapor is passed through a red-hot tube 
it is decomposed, yielding the chlorides C^Cl* and C'^CP. 

When heated with aluminium iodide, AlP, carbon tetra- 
chloride is converted into carbon tetraiodide, CP, which sepa- 
rates from its ethereal solution in dark-red regular octahedra 
(Gustavson). 

METHYL CYANIDE, OR ACETONITRILE. 

C-^H^'N^ CH3.cn 

This body may be obtained by distilling a mixture of potas- 
sium methylsulphate and potassium cyanide, or by distilling 
acetamide with phosphoric anhydride, which removes one mol- 
ecule of water from the former body. 



METHYL NITRITE AND NITROMETHANE. 493 

Acetamide. Methyl cyanide, or acetonitrile. 

Methyl cyanide is a colorless liquid, having a disagreeable 
odor; it boils at 81.3°. A boiling solution of potassium hy- 
droxide decomposes it into ammonia and potassium acetate. 
CH^-CN + 2H^0 = CH^-CO.OH + NH^ 

Methyl cyanide. Acetic acid. 

G-autier has discovered an isomeride of methyl cyanide, 
methyl carhylamine. This body is formed, together with 
methyl cyanide, when a mixture of potassium methylsulphate 
and potassium cyanide is distilled. Under the influence of alka- 
lies, it decomposes into formic acid and methylamine. 

(.g3 } N -f KOH -f H^O = KCHO^ + ^h' } ^ 

Methyl carbylamine. Potassium formate. Methylamine. 

The trinitro-derivative of methyl cyanide, C(NO^)^CN, is 
called trinitro-acetonitrile. It is a white, camphor-like mass, 
melting at 41.5°, and exploding at 200°. 

METHYL NITRATE. 

CH3.N03 

This substance, which represents nitric acid in which the 
basic hydrogen is replaced by methyl, is an example of a com- 
pound methyl ether. 

It is prepared by introducing into a retort 50 grammes of 
powdered potassium nitrate, and adding a mixture of 100 
grammes of sulphuric acid and 50 grammes of wood-spirit. 
The reaction begins in the cold, but must be finished by dis- 
tilling on a water-bath. The liquid condensed in the receiver 
is washed with water, and rectified several times over a mix- 
ture of massicot and calcium chloride. 

It is a colorless, neutral liquid ; density, 1.182 ; boiling-point, 
66°. Its vapor explodes violently when heated above 150°. 

Methyl nitrate dissolves in ammonia, producing ammonium 
nitrate and methylamine. 

CHINO^ + 2NH3 = NmNO^ -f CH^(Nff) 

METHYL NITRITE AND NITROMETHANE. 

These two compounds present a remarkable instance of 
isomerism in very simple combinations. 

The first, CH^O.NO, which represents nitrous acid, HNO^, 
42 



494 ELEMENTS OF MODERN CHEMISTRY. 

in wliicli the hydrogen is replaced by methyl, is obtained when 
methyl alcohol is heated with nitric acid in presence of copper. 
It is a liquid boiling at about — 12°. 

The second, called also nitrocarhol^ represents methane, in 
which an atom of hydrogen is replaced by the group (NO^)'. 
CH* Cff(NO^) 

Methane. Nitromethane. 

It is obtained by the action of potassium nitrite upon potas- 
sium monochloracetate (Kolbe). 

CH»C1.C02K + KN02 + H20 = KCl + CH3(N02) + KHCQS 
Potassium mono- Potassium Nitromethane. 

chloracetate. nitrite. 

It is also produced by the action of silver nitrite on methyl 
iodide (Y. Meyer). 

Nitromethane is a liquid boiling between 101 and 102°. It 
has an acid character, and one of its hydrogen atoms may be 
replaced by sodium. 

Nitromethane is clearly distinguished from methyl nitrite by 
the following property : nascent hydrogen transforms nitrome- 
thane into methylamine, a reaction which does not take place 
with its isomeride. 

CHXNO'O + 3H2 =:=: CHlNff + 2>W0 

Nitromethane. Methylamine. 



METHYLNITROLIC ACID. 

CH2N203==CH<:^^'2 

This remarkable combination has been obtained by Y. Meyer 
by the action of nitrous acid upon nitromethane. 

CH^NO^) + NO.OH = CH(x^^^jj + H^O 

It is seen that in this compound two atoms of hydrogen of 
the methyl group CH^, are removed by an atom of oxygen of 
the nitrous acid, and replaced by the residue (N.OH). 

Methylnitrolic acid is prepared by dissolving 5 grammes of 
nitromethane in water, and adding first a dilute solution of 
potassium nitrite cooled to 0°, then dilute sulphuric acid also 
cooled to 0°, and finally dilute solution of potassium hydrate 
as long as the red color persists. At this moment, sulphuric 
acid is again added until the liquid is decolorized ; the solution 
is then saturated with calcium carbonate, and agitated with 
ether, which dissolves the methylnitrolic acid. 



FULMINATES OF MERCURY AND SILVER. 495 

After tlie evaporation of the ether, the acid remains as large, 
transparent, colorless prisms, fusible at 54°, but decomposing 
at the same time into formic acid and nitrogen. Dilute sul- 
phuric acid decomposes methylnitrolic acid into formic acid and 
nitrogen monoxide. 

CHWO^ = CH^O^ + N^O 

Formic acid. Nitrogen monoxide. 

The crystals decompose spontaneously in a few days. 



FULMINATES OF MEKCURY AND SILVER. 

Among the important compounds related to the more simple 
organic combinations are those explosive salts known as fulmi- 
nates of mercury and silver. 

They are obtained by dissolving mercury or silver in nitric 
acid and adding alcohol to the still hot solution. In a few 
minutes a brisk effervescence takes place, and fulminate of 
mercury or of silver is deposited as a white, crystalline precip- 
itate. When dry, these bodies explode violently by either heat 
or percussion. Fulminate of mercury is the basis of percus- 
sion-caps. 

The composition of these salts is interesting. They are 
derived from fulminic acid^ a body which is isomeric with 
cyanic acid (Liebig, Gay-Lussac). According to Kekule, ful- 
minic acid is nitro-acetonitrile, CH^(NO^).CN, that is methane 
in which one hydrogen atom is replaced by the monatomic 
group NO^ and a second one by the cyanogen group (CN). 
More recent investigations by Nef and others make it appear 
probable, however, that it is carbj/loxime, C = NOH, in which 
a diatomic carbon atom is united with the group N = OH, 
which characterizes a large and important class of carbon 
compounds known as the oximes (page 554). 

In fulminate of mercury one atom of metal replaces two 
atoms of hydrogen in two molecules of the acid, while in the 
silver salt the metal replaces hydrogen atom for atom : the 
formula of mercury fulminate is 2C^N^0^Hg -f- H^O, and that 
of the silver salt C'N^O'Ag^ 

Free fulminic acid results when these compounds are decom- 
posed by strong acids. Its odor resembles that of hydrocyanic 
acid, and, like the latter, it is very poisonous. Upon heating 
with hydrochloric acid, it yields formic acid and hydroxylamine. 



496 ELEMENTS OF MODERN CHEMISTRY. 

CACODYL, OR DIMETHYLARSINE. 

As2(CH3)4 

This interesting compound has long been known in an im- 
pure state, having been first obtained in 1760 by Cadet as a 
product of the distillation of a mixture of potassium acetate 
and white arsenic (arsenious oxide). He collected in the re- 
ceiver an oily liquid, having an extremely offensive odor, and 
producing dense white fumes in the air. Hence the name 
fuming liquor of Cadet. 

Bunsen's investigation into the chemistry of this body and 
its combinations has become classic. According to his re- 
searches, the fuming liquor of Cadet is a mixture of two bodies, 
one of which, containing only carbon, hydrogen, and arsenic, 
plays the part of a radical : it is cacodyl ; the other body is the 
oxide of this radical. 

To obtain cacodyl in the pure state, the crude product is 
treated with hydrochloric acid, which converts the oxide of 
cacodyl into chloride. 

As^CCH^yO -f 2HC1 =z 2As(CH^)'Cl + WO 

Dimethylarsine oxide. Dimethylarsine chloride. 

This chloride, separated by distillation, and treated with zinc 
at 100° in sealed tubes, furnishes free cacodyl. 

The latter is a dense liquid boiling at 170°, and having a 
penetrating arsenical odor. It is very poisonous. It produces 
dense white fumes in the air, even taking fire spontaneously. 
Its vapor density is 7.101. 

According to this vapor density, free cacodyl is diarsenic 
tetramethyl, As^CH^)* = (CH=^)'As-As(Cff )^ 

Arsenic being either triatomic or pentatomic it is seen that 
cacodyl is not saturated; hence it can directly fix chlorine, 
oxygen, etc., yielding two series of compounds. Thus, one 
molecule of cacodyl, As^(CH^)*, can fix 1 or 3 molecules of 
chlorine, forming the two chlorides : 

As2(CH3)4 + C12 = 2As(CH3)2Cl 
As2(CH3)4 + 3C12 = 2As(CH3)2Cl3 

To the two chlorides correspond the bromides, iodides, oxides, 
sulphides, etc. The oxides are 

Cacodyl oxide [As(CH3)2]'20 
Cacodylic acid As(CH3)20.0H 



ETHYL COMBINATIONS. 497 

Independently of the cacodyl compounds, other combinations 
of arsenic and methyl are known, — the metliylarsines and the 
compounds of methylarsonium. 

These bodies form two series, which were discovered and 
studied by Baeyer, and which belong to the type AsX^ and 
AsX^. The compounds of the first kind are not saturated, and 
can combine with CP, or the equivalent of CP, passing into the 
state of the saturated compounds of the series AsX^. 



Series AsX^ 


Series AsX^ 


As(CH3)3 
Triraethylarsine. 


As(CH3)4Cl 
Tetramethylarsonium chloride. 


As(CH3)2Cl 
Dimethylarsine monochloride. 


As(CH3)3C12 
Triraethylarsine dichloride. 


As(CH3)Cr-^ 
Mouomethylarsine dichloride. 


As(CH3)2Cl3 
Dimethylarsine trichloride. 


AsCls 
Arsenic trichloride. 


As(CH3)Cl* 
Monomethylarsine tetrachloride. 




[AsCl5] 



It is worthy of remark that the trichloride of arsenic is 
incapable of fixing CP, and passing into the state of penta- 
chloride, although the corresponding fluoride, AsF^, is known. 

These compounds need not be described. It may only be 
mentioned that trimethylarsine, As(CH^)^, is formed, together 
with cacodyl, by the action of methyl iodide on sodium arsenide. 
It is a liquid boiling below 100°. 



ETHYL COMBESTATIONS. 

The monatomic residue (C'H^)' = C'H« — H, which is the 
radical of ordinary alcohol, is called ethyl. Numerous com- 
pounds are known into which the radical enters. 

When combined with hydrogen, it forms a gas, C^H®, which 
is ethyl hydride or ethane. The chloride, bromide, iodide, and 
cyanide of ethyl were formerly designated as simple ethers. 

C2H5C1 ethyl chloride. 

C2H5Br ethyl bromide. 

C2H5I ethyl iodide. 

C3H5.cn ethyl cyanide. 

Ordinary alcohol is the hydroxide, ether is the oxide of 
ethyl. 

C2H5-OH ethyl hydroxide (alcohol). 

C2H5-0-C2H5 = (C2H5)20 ethyl oxide (ether). 
99 42* ,_ 



498 ELEMENTS OF MODERN CHEMISTRY. 

The neutral compound ethers are derived from the corre- 
sponding acids by the substitution of the radical C'^H^ for their 
basic hydrogen. 

C2H30-OH C2H30-OC2H5 

Acetic acid. Ethyl acetate. 



I OH ^ "" 1 O.C2H5 

Oxalic acid. Ethyl oxalate. 

roH ro.c^Hs 

PO^^OH PO^O.C2H5 

(OH i0.C2H5 

Phosphoric acid. Phosphoric ether (triethyl phosphate). 

Free Ethyl, or Butane, C*H^''. — When it is sought to obtain 
free ethyl by heating ethyl iodide to 150° with zinc in sealed 
tubes, the radical combines with itself, its molecule being doubled 
(Frankland). 

2C2H5I + Zn =: ZnP + (C^H^)^ 

A gas is thus formed which liquefies at -|-1°- It was 
formerly named free ethyl, but is the hydride of butyl, or 
butane. Indeed, it is incapable of regenerating ethyl compounds 
containing the simple radical (C^H^). When treated with bro- 
mine, it yields hydrobromic acid and a bromide C*H^Br^, which, 
according to Carius, is identical with butylene bromide. 

Ethyl Hydride, Ethane, or Dimethyl, C^H« = CH^-CH^ 
— Frankland obtained this gas by treating zinc-ethyl with 
water. 

ZniQ'Wy + 2W0 = 2.Q'W + Zn(0H)2 

Zinc ethyl. Ethane. Zinc hydrate. 

It is likewise formed when methyl iodide is heated with 
sodium in closed tubes. 

2QW1 + 2Na = C^H^ + 2NaI 

It is a colorless gas, burning with a slightly blue, luminous 
flame. When treated with chlorine, it yields ethyl chloride 
and hydrochloric acid. 

ETHYL HYDROXIDE, OR ALCOHOL. 
C2H60 = CH3-CH2.0H 

Alcohol is the product of the fermentation of solutions which 
contain glucose, or a substance capable of transformation into 
glucose. 

It may be formed synthetically in various manners : 

1. By passing ethylene gas into sulphuric acid (Hennell and 



ETHYL HYDROXIDE. 499 

Faraday) and boiling the ethylsulphuric acid so formed (Ber- 
thelot). 



Ethylene. Ethylsulphuric acid. 

Ethylsulphuric acid. Alcohol. 

2. By heating ethylene gas with hydriodic acid and decom- 
posing the ethyl iodide so formed with potassium hydroxide 
(Berthelot). 

C^H* + HI = C'Wl 

C^ffl + KOH = en^OH + KI 

3. By bringing aldehyde in contact with sodium amalgam in 
presence of water. The nascent hydrogen formed in this case 
fixes upon the aldehyde, converting it into alcohol (A. Wurtz). 

C^H^O -f H^ = C^H^O 

Aldehyde. Alcohol. 

Preparation and Purification of Alcohol. — Alcohol is 
manufactured by distilling fermented liquors, such as wine, 
fermented juice of beet-roots, and the product obtained from 
the fermentation of malt, which is saccharified barley, corn, or 
other grain. The apparatus now used for this operation has 
reached such a degree of excellence that alcohol of 95 per cent, 
may be obtained immediately by one distillation. 

Absolutely pure alcohol is obtained by rectifying the alcohol 
of commerce over hygroscopic substances, such as anhydrous 
potassium carbonate, quick-lime, or caustic baryta. The last 
portions of water are removed, and absolute alcohol obtained 
by redistilling the rectified alcohol with caustic baryta. Or 
some sodium may be dissolved in the alcohol, which may then 
be rectified on a water-bath. 

Properties. — Alcohol is a colorless, mobile liquid, having an 
agreeable, spirituous odor. Density at 0°, 0.8095. BoiHng- 
point, 78.4° at the normal pressure. It freezes at — 130°. 

Alcohol mixes with water and ether in all proportions. Its 
mixture with water takes place with elevation of temperature 
and contraction of volume. The maximum contraction takes 
place when the two bodies are mixed in the proportion of one 
molecule of alcohol (46 parts) to three molecules of water (54 
parts). 



500 ELEMENTS OF MODERN CHEMISTRY. 

Alcohol absorbs moisture wben exposed to tbe air. It dis- 
solves many gases, liquids, and solids. Tinctures are solutions 
of various medicinal substances in alcohol. 

Among the simple bodies which are soluble in alcohol may- 
be mentioned iodine. Potassium and sodium hydroxides dis- 
solve in it readily, and the same is true of many of the mineral 
acids. Many of the chlorides are soluble in alcohol ; such are 
those of calcium, strontium, zinc, and cadmium, ferric, cupric, 
mercuric, and auric chlorides. 

Alcohol dissolves the natural alkaloids, the essential oils, 
resins, and fatty bodies, the latter, however, less readily than 
ether. 

Decompositions. — When vapor of alcohol is passed through 
a red-hot porcelain tube, it is decomposed into water, carbon 
monoxide, hydrogen, methane, and ethylene. Besides this, 
carbon is deposited in the porcelain tube, and a small quantity 
of naphthalene is produced (Th. de Saussure), as well as 
benzene and phenol (Berthelot). The principal products of 
the decomposition of alcohol at a dull-red heat are methane, 
hydrogen, and carbon monoxide. 

(JWO = CO + CH^ + H^ 

On the application of a burning body, alcohol takes fire 
and burns with a slightly luminous, bluish flame. On contact 
with platinum black, alcohol vapor mixed with air undergoes a 
slow combustion, which produces successively aldehyde and 
acetic acid. 

C^H^O + = C^H*0 -f H^O 

Alcohol. Aldehyde. 

Q'WO + = C'H^O' 

Aldehyde. Acetic Acid. 

Acetic ether and a small quantity of a volatile, neutral body, 
called acetal, are at the same time formed as accessory products 
(Stas). 

The lamp without flame of Dobereiner depends upon the 
slow combustion of alcohol. The wick of an ordinary spirit- 
lamp is surmounted by a spiral of platinum wire, so that when 
the lamp is lighted the spiral is heated to incandescence. If 
then the flame be extinguished, by covering it for an instant 
with a test-tube, the alcohol vapor continues to rise with the 
air around the still hot spiral, and undergoes a slow combustion. 
But the latter develops heat, and the spiral rapidly becomes 



ETHYL HYDRATE. 501 

heated to incandescence, and if the current of air be regulated 
by a small glass chimney, the experiment may continue as long 
as the wick emits vapor of alcohol in sufficient quantity. 

Bodies rich in oxygen oxidize alcohol at ordinary tempera- 
tures ; such are chloric and chromic acids. If a little alcohol 
be poured upon some chromic acid placed upon a brick, the 
liquid is immediately inflamed and the chromic acid reduced 
to chromium oxide. 

Chlorine attacks alcohol with great energy, the final product 
of the reaction being a body which has received the name 
chloral (Liebig, Dumas). 

If a small piece of potassium or sodium be thrown into pure 
alcohol, the metal soon melts, and then dissolves with disen- 
gagement of hydrogen. The product of the reaction is a crys- 
talline, solid matter which is ethylate of potassium or sodium, 
that is, a body derived from alcohol by the substitution of an 
atom of an alkaline metal for an atom of hydrogen. 

C2H5^ C2H5^ C2H5^ 

H>^ K-^^ Na>^ 

Alcohol. Potassium ethylate. Sodium ethylate. 

Uses of Alcohol. — Alcohol is used as a combustible in spirit- 
lamps. In the arts, it is employed in the manufacture of ether, 
chloroform, perfumeries, and many other products. It is 
largely used in the laboratory, and in pharmacy, as a solvent ; 
it serves for the preservation of anatomical specimens. In 
France and England, alcohol employed for certain industrial 
uses is exempted from part of the tax, when it has previously 
been mixed with about one-tenth of wood-spirit and a few 
per cent, of mineral oils and resin. Such a mixture is unfit 
for the manufacture of brandy and liquors, but its usefulness 
as a solvent is in most cases unimpaired. 

Alcohol exists in fermented liquors, such as wine, cider, and 
beer. It is contained in much larger quantities in brandies, 
whiskeys, and spirits. These are products of the distillation of 
various alcoholic liquids. They are more or less rich in alco- 
hol. Brandy is prepared by the distillation of wine, cider, or 
the products of fermentation of cherry-juice (cherry-brandy), 
sugar-cane (rum), beet-root molasses (beet-brandy). Whiskey 
is distilled from fermented starchy materials, such as corn, rye, 
potatoes, etc., the starch being first saccharified. The richness 
of these materials in alcohol is indicated by the degrees of an 



502 ELEMENTS OF MODERN CHEMISTRY. 

alcoholometer. The following table gives the strength of 
some of these liquors. (For wine, beer, etc., see page 648). 

BATTM^'S SPECIFIC ^"^^^^^'hOL "" 

HYDROMETER. GRAVITY. ^y VOLUME. 

Weak brandy 16° 0.9605 37.9 

Proof spirits 19° 0.9420 60.1 

Strong brandy 22° 0.9241 59.2 

Ordinary alcohol .34° 0.8688 86.1 

Rectified alcohol (strongest commercial) 40° 0.8296 95. 

Absolute alcohol 46° 0.8095 100. 

ETHYL OXIDE, OR ETHEE. 

(C2H5)20 = OH3-CH2-0-CH2-CH3 

If ethyl iodide be added to an alcoholic solution of ethylate 
of sodium and a gentle heat be applied, a deposit of sodium 
iodide is formed and vapors are disengaged which may be con- 
densed in a cooled receiver into an ethereal liquid. It is 
oxide of ethyl. 

Cm^I + <''§l>0 = Nal + gHJ>o 

Ethyl iodide. Sodium ethylate. Ethyl oxide. 

If, in the preceding experiment, the ethyl iodide be replaced 
by methyl iodide, an extremely volatile liquid will be formed, 
which is the double oxide of methyl and ethyl. 

CH3I + <^§l>0 = Nal + %^l>0 

Methyl iodide. Oxide of methyl and ethyl. 

These classic experiments, due to Williamson, show that 
the oxide of ethyl contains two ethyl groups. It may be 
regarded as alcohol in which the hydrogen atom of the group 
hydroxyl is replaced by ethyl. 

H-O-H C2H5-0-H C2H5-0-C2H5 

Water. Alcohol. Ethyl oxide. 

Ether may also be obtained by the action of ethyl iodide on 
silver oxide. 

Preparation. — Ether is prepared in the arts by the action 
of sulphuric acid on alcohol. A mixture of 9 parts of con- 
centrated sulphuric acid and 5 parts of alcohol of 90 per cent, 
is heated in a flask, A (Fig. 126), and a small, continuous 
stream of alcohol is allowed to flow into this mixture through 
the funnel-tube a. The temperature of the liquid, indicated by 
the thermometer t, should not exceed 140 or 145°. The vapor 
disengaged is condensed in a Liebig's condenser, B, through 



ETHYL OXIDE. 



503 



which a stream of cold water flows continually. Under these 
conditions, a mixture of ether and water collects in the re- 
ceiver D, together with a little alcohol, and towards the close 
of the operation, a small quantity of sulphurous acid gas is 
disengaged. The product is purified by washing with milk of 
lime, and then with pure water, after which it is rectified over 
calcium chloride on a water-bath. Fig. 126 represents the 
apparatus used for public demonstration ; in the arts, the opera- 
tion is conducted on a large scale in apparatus of an analogous 
construction. 




Fig. 126. 



Theory of Etherification. —The transformation of alcohol 
into ether is a true dehydration, brought about by the sul- 
phuric acid. 

2(C^ff .OH) = (C^H^yO + H^O 

Williamson clearly proved that it is effected in two distinct 
phases ; in the first, ethylsulphuric acid and water are formed. 

Ethylsulphuric acid. 



C^H^>0 



Alcohol. 

In the second, another molecule of alcohol reacts with the 
ethylsulphuric acid; ether is formed and sulphuric acid is 
yegenerated. 



504 ELEMENTS OF MODERN CHEMISTRY. 

jj>bO* + jj>0 = C2H5>^ + H-^^^ 
Ethylsulphuric acid. Alcohol. Ether. Sulphuric acid. 

Hence the ether and water collected in the receiver are pro- 
ducts of two distinct phases of the reaction. Ethylsulphuric 
acid is continually formed and as continually decomposed, 
regenerating sulphuric acid ready to act upon new por- 
tions of alcohol. However, although the operation is con- 
tinuous, it cannot go on indefinitely : the mixture blackens ; 
while the acid is being diluted continually with water formed 
in the first phase of the reaction, it is also in part reduced 
by the alcohol, sulphur dioxide being formed. 

Properties of Ether. — Ether is a colorless, very mobile 
liquid ; its taste is at first burning, then cooling ; its odor is suave 
and agreeable, and is called ethereal. Density at 0°, 0.7366. 
Boiling-point under the normal pressure, 34.5°. 

It is but slightly miscible with water, on the surface of which 
it forms a separate layer. 9 parts of water dissolve 1 part of 
ether ; 36 parts of ether dissolve 1 part of water. Ether dis- 
solves in all proportions in alcohol and in methyl alcohol. 

It slightly dissolves sulphur and phosphorus, and notable 
quantities of bromine, iodine, ferric, mercuric, and auric chlo- 
rides, and many organic bodies, such as the oils, fats, resins, 
alkaloids, etc. 

In 1846, Dr. William T. G. Morton, of Boston, discovered 
the fact that ether vapor when inhaled produces unconscious- 
ness and anaesthesia. This discovery has been of inestimable 
value in surgery, and while other anaesthetics, such as chloro- 
form, have been introduced, ether still seems to have the 
general preference. 

It is very inflammable and burns with a quite luminous 
flame. Its vapor explodes violently when mixed with air or 
oxygen and ignited. 

If a heated spiral of platinum wire be suspended in a glass 
jar containing a little ether, in such a manner that the lower 
extremity of the wire is but a little distance from the surface 
of the liquid, the wire will soon become brightly incandescent 
and will ignite the ether. This eff'ect is due to the ether vapor, 
which, coming in contact with the platinum, and being mixed 
with air, undergoes a slow combustion. Heat is thus developed, 
and the wire becomes incandescent. 

Ohlorine acts on ether with extreme energy. If the a-ctiou 



HYDROSULPHIDE AND SULPHIDE OF ETHYL. 505 

be moderated, various products of substitution are obtained, 
among which the following have been well studied : 

Monochloretlier ^^^^^^'^0 liquid boiling at 98-99°. 

DicMorether ^^%%'>0 liquid boiling at 140-147°. 

Tetrachlorether q2jjzcI'^^^ liquid, density 1.5. 

r;2r;i5 
PercMorether 02015-^^ colorless crystals, fusible at 69°. 

The last is a solid body, crystallizing in octahedra. By the 
action of heat it is decomposed into carbon sesquichloride and 
perchloraldehyde (Malaguti). 

C2C15>^ = C2C16 + C2C1*0 

Perchlorether. Carbon sesquichloride. Perchloraldehyde. 

When two parts of bromine are added to one part of ether, 
and the mixture is cooled, a garnet-colored compound of bro- 
mine and ether, (C^H^)^O.Br'^, separates. It crystallizes in thin 
plates, fusible at 22°, and is easily decomposed (Schtitzen- 
berger). 

HYDROSULPHIDE AND SULPHIDE OF ETHYL. 

Two bodies are known which are intimately related, as re- 
gards their constitutions, with alcohol and ether. They are 
the hi/ dro sulphide and the sulphide of etliyl. The first, formerly 
known as mercaptan^ represents alcohol containing an atom of 
sulphur instead of an atom of oxygen ; the second represents 
ether in which the oxygen atom is replaced by sulphur. 

C^ff.OH (C^H^)^O 

Ethyl hydroxide. Ethyl oxide. 

C^H^SH (C^ff)^S 

Ethyl hydrosulphide. Ethyl sulphide. 

Ethyl hydrosulphide is obtained by distilling a concentrated 
aqueous solution of potassium hydrosulphide with a solution 
of potassium ethyl sulphate. 

It may also be prepared by passing vapor of ethyl chloride 
into an alcoholic solution of potassium hydrosulphide. The 
liquid is distilled as soon as it is saturated with ethyl chloride, and 
water is added to the distillate. Ethyl hydrosulphide separates. 

KSH -h C^H^Cl -= KCl + C'^H^SH 

Potassium hydrosulphide. Ethyl chloride. Ethyl hydrosulphide. 

W 43 



506 ELEMENTS OP MODERN CHEMISTRY. 

Ethyl hydrosulphide is a transparent, colorless liquid, very 
mobile, and having a fetid odor. Density at 21°, 0.835. 
Boiling-point, 36.2° (Liebig). 

It reacts energetically with mercuric oxide, forming water 
and a white, crystalline body which represents ethyl hydros 
sulphide in which the hydrogen is replaced by mercury. 
Hence the name mercaptan (niercurium captans) given to the 
hydrosulphide of ethyl by Zeise. This mercuric compound is 
insoluble in water j it contains (C^H^S)^Hg". 

Ethyl sulphide is obtained, like the hydrosulphide, by double 
decomposition. Vapor of ethyl chloride is passed into an alco- 
holic solution of potassium monosulphide. 

K^S -f 2C^ffCl = 2KC1 + (C'H^)2S 

Potassium sulphide. Ethyl chloride. Ethyl sulphide. 

Ethyl sulphide is a colorless liquid, having a garlicky odor. 
It boils at 91°. It is insoluble in water. 



ETHYL CHLORIDE. 

C2H5C1 

This body is prepared by saturating alcohol with hydrochloric 
acid gas and distilling on a water-bath. Ethyl chloride is dis- 
engaged, and should be passed first through a wash-bottle and 
then through a tube containing calcium chloride, after which it 
may be condensed in a receiver placed in a freezing mixture. 

Below 12.5°, its boiling-point, ethyl chloride is a mobile, 
colorless liquid, having a penetrating and agreeable odor. It 
is inflammable, and burns with a flame tinged with green. 

If some solution of silver nitrate be agitated in a jar con- 
taining vapor of ethyl chloride, no precipitate will be formed; 
but if the agitation be continued after the vapor has been 
ignited, an abundant precipitate of silver chloride will be 
formed, owing to decomposition of the silver nitrate by the hy- 
drochloric acid produced by combustion of the ethyl chloride. 

Ethyl chloride produces a precipitate of silver chloride when 
passed into an alcoholic solution of silver nitrate. 

Chlorinated Derivatives of Ethyl Chloride. — When ethyl 
chloride is submitted to the action of chlorine, various com- 
pounds are successively formed by the substitution of chlorine 
for hydrogen, atom for atom. The following is the nomencla- 



ETHYL BROMIDE. 507 

ture and composition of these chlorinated compounds, which 
were discovered by V. Regnault. 

C2H5C1 ethyl chloride. 

C2H*C12 dichlorethane (ethylidene chloride)— boils at 57.5°. 

C2H3CP trichlorethane— boils at 75°. 

C'^H2C14 tetrachlorethane— boils at 127.5°. 

C2HC15 pentachlorethane— boils at 158°. 

C^Cl^ hexachlorethane (sesquichloride of carbon). 

It will be noticed that the second of these compounds is 
isomeric with ethylene chloride, or Dutch liquid, of which the 
description will be found farther on. It may be obtained by 
treating aldehyde with phosphorus pentachloride. 

CH^-CHO -\~ POP = CH^-CHCP + POCP 

Aldehyde, Dichlorethane. Phosphorus oxychloride. 

This mode of formation indicates its constitution, which is 
expressed by the formula 

C!HCP 
To distinguish it from its isomeride ethylene chloride, 
CffCl 

CH^Cl 
it is named dichlorethane or ethylidene chloride. 

In the sesquichloride of carbon, C^CP, the hydrogen atoms 
are all replaced by chlorine. Carbon sesquichloride is a crys- 
talline solid, melting at 187°, and boiling at 200°-210° 

ETHYL BROMIDE. 

C2H5Br 

Ethyl bromide is prepared by distilling a mixture of alcohol, 
bromine, and amorphous phosphorus, or a mixture of potassium 
bromide, alcohol, and sulphuric acid diluted with its own volume 
of water. In either case the distillate is washed with water, 
and the oily ethyl bromide separated and dried with potassium 
carbonate. 

It is a colorless, refracting liquid, having an odor resembling 
that of chloroform, and a burning taste. It mixes in all pro- 
portions with alcohol and ether, but is insoluble in water. Its 
density at 15° is 1.4189, and it boils at 40.7°. 

It has been employed to a limited extent as an anaesthetic. 



508 ELEMENTS OF MODERN CHEMISTRY. 

ETHYL IODIDE. 
C^Hsi 

This important compound is prepared by the action of alco 
hoi on iodine in presence of amorphous phosphorus. Phos- 
phorus iodide is formed, and reacts upon the alcohol, yielding 
ethyl iodide and an acid of phosphorus. The former distils 
into the receiver, together with the alcohol which escapes the 
reaction. AVater is added, and the lower layer of liquid is 
separated, dried with calcium chloride, and rectified on a water- 
bath. 

Ethyl iodide is a colorless liquid, but becomes brown when 
long kept, especially when exposed to light. Density at 0°, 
1.9753. Boiling-point, 72.2°. 

It can exchange its iodine by double decomposition, as can 
potassium iodide. If ethyl iodide be added to an alcoholic 
solution of silver nitrate, a yellow precipitate of silver iodide 
is at once formed, while ethyl nitrate remains in solution. 

C'H^I + AgNO^ = Agl + (C^H^)NO^ 

Ethyl iodide. Silver nitrate. Ethyl nitrate. 

ETHYL CYANIDE. 
C3H5N = CH3-CH2-CN 

This compound is formed when ammonium propionate is 
distilled with phosphoric anhydride. 

(NH*)C3H50^ = C^H^N + 2W0 

Ammonium propionate. Ethyl cyanide. 

From this mode of formation, ethyl cyanide is sometimes 
called propionitrile. The same body exists in the product of 
the distillation of a mixture of potassium cyanide and potassium 
ethylsulphate. 

KCN -h ^^^^>S04 = K^SG* -f C2H5.cn 

Potassium Potassium Potassium Ethyl cyanide, 

cyanide. ethylsulphate. sulphate. 

But this product, which is liquid and has a variable boiling- 
point, contains, independently of the true cyanide of ethyl, an 
isomeride of that body, whose existence was foreseen by Meyer, 
and discovered by Gautier in the product of the action of 
ethyl iodide on silver cyanide. 



NITROETHANE AND ITS DERIVATIVES. 509 

Ethjl cyanide is a colorless liquid, having a penetrating and 
pleasant odor. It boils at 96.7°. 

When it is boiled with potassium hydroxide, potassium pro- 
pionate is formed and ammonia is disengaged (Dumas, Mala- 
guti, and Le Blanc). 

effN + KOH + H^O = KC^H^O^ + NH^ 

Ethyl cyanide. Potassium propionate. 

When ethyl cyanide is brought into contact with dilute sul- 
phuric acid and zinc, it fixes 4 atoms of hydrogen and is 
converted into propylamine (Mendius). 

C^H^N -I- H* = en^N 

Ethyl cyanide. Propylamine. 

Ethylcarbylamine. — This name was given by Gautier to the 
isomeride of ethyl cyanide already mentioned. It is a color- 
less liquid, having a very penetrating and intensely offensive 
odor. It boils at 79°. With potassium hydroxide it yields 
potassium formate and ethylamine. 

C2H5-^ + K0H + H20= H-^N + KCHO2 

H -^ 

Ethylcarbylamiae. Ethylamine. Potassium 

formate. 

ETHYL NITRITE, OR NITROUS ETHER. 
C2H5.0-NO 

This compound is obtained by the action of nitric acid on 
alcohol. The reaction is very violent, and abundant red vapors 
are evolved. After passing through a wash-bottle, they are 
conducted into a well- cooled receiver, where the ethyl nitrite 
condenses. 

It is a yellowish, very volatile liquid, whose odor recalls that 
of apples. It boils at 18°. It is but slightly soluble in 
water. Hot water immediately decomposes it into alcohol and 
nitrous acid, the latter being itself decomposed into nitric acid 
and nitric oxide. 



NITROETHANE AND ITS DERIVATIVES. 

C2H5-N02 

This isomeride of ethyl nitrite represents ethane, C^H^, in 
which one atom of hydrogen is replaced by the group (NO^)'. 
It is the higher homologue of nitromethane. 

43* 



510 ELEMENTS OP MODERN CHEMISTRY. 

It is obtained, together with a certain quantity of etliyl 
nitrite, when ethyl iodide is treated with silver nitrite. 

C^H^I + AgNO^ = C^H^CNO^) + Agl 

Ethyl iodide. Silver nitrite. Nitrethane. 

It is a liquid having a peculiar, ethereal odor and boiling at 
113-114°. Density at 13°, 1.0582 (V. Meyer). 

With nascent hydrogen, it furnishes pure ethylamine. 

All of the homologues of nitroethane thus yield the corre- 
sponding amines. It is a general character of the nitro com- 
pounds, and one which is not possessed by their isomerides, 
the nitrous ethers. In constitution and properties, nitroethane 
approaches nitrobenzene, as will be seen by the following 
comparison of their formulae : 

Ethane. Benzene. 

Nitroethane. Nitrobenzene. 

Ethylamine. Phenylamine (aniline). 

The presence of the group (NC^) confers acid properties 

upon nitroethane. Its sodium compound, C^H*<^^ , is formed 

either by the action of an alcoholic solution of sodium hydrate 
on nitroethane, or by the direct action of sodium on the same 
body ; in the latter case hydrogen is disengaged. Sodium- 
nitroethane is very explosive (Y. Meyer and Stuber). 

When it is sought to prepare potassium-nitroethane by the 
action of alcoholic potassium hydrate on nitroethane, the 
latter body is decomposed, yielding, among other products, 
potassium nitrite. Now, the latter salt exerts a remarkable 
action on nitroethane, giving rise to a new body of complex 
composition, potassium ethylnitrolate. 

Ethylnitrolic acid may be obtained by a process analogous to 
that which has been described for the preparation of methyl- 
nitrolic acid. Ethylnitrolic acid contains 

C=N.OH 



ETHYL NITRATE— ETHYL StJLPHATE. 511 

It crystallizes in light-yellow, transparent prisms, possessing 
a feeble bluish fluorescence and a very sweet taste. It decom- 
poses without violence at 81-82° into nitrogen, nitrous vapors, 
and acetic acid. When boiled with dilute sulphuric acid, it 
decomposes into acetic acid and nitrogen monoxide. 

Ethylnitrolic acid. Acetic acid. 

ETHYL NITRATE, OR NITRIC ETHER. 

(C2H5)N03 

This is obtained by the action of nitric acid upon alcohol in 
presence of a small quantity of urea. The latter body prevents 
the reduction of the nitric acid to nitrous acid. Nitric ether 
condenses in the receiver. It is washed with water, dehydrated 
with calcium chloride, and rectified. It is a liquid, having an 
agreeable, ethereal odor. It boils at 86°. Density at 0°, 1.1322. 

Potassium hydroxide decomposes it, like all compound 
ethers, forming potassium nitrate and alcohol. 

(C^H5)N0^ + KOH = C^H^OH + KNO^ 

It dissolves in ammonia, especially if the latter be warm, 
yielding ammonium nitrate and ethylamine. The reaction is 
analogous to that of ammonia upon methyl nitrate. 

ETHYL SULPHATES. 
Ethylsulplmric or Sulphovinic Acid. — tj [ SO* = 

Q2JJ5Q Jtl j 

TT^^-SO^. This body is an example of an acid ether. It 

results from the substitution of a single ethyl group for one 
atom of hydrogen in sulphuric acid, which is dibasic. 

I j sov ^' H>^^* 

It is formed by the action of sulphuric acid upon alcohol. 
The mixture of the two bodies becomes hot, and if after cool- 
ing the liquid be diluted and saturated with barium carbonate, 
an abundant precipitate of barium sulphate will be formed, and 
a soluble salt of barium, the ethylsulphate, will remain in solu- 
tion. A solution of ethylsulphuric acid may be obtained by 
exactly decomposing this salt with dilute sulphuric acid. 



512 ELEMENTS OF MODERN CHEMISTRY. 

By boiling, ethylsulphuric acid is decomposed into sulphuric 
acid and alcohol. 

The ethylsulphates are beautiful salts ; they are crystalliz- 
able and soluble in water. 

p2TT5 ^ r2TT5 n 

Ethyl Sulphate.— ^2^5 1 SO^ = q'2^^'^>^0\ This 

body, which represents sulphuric acid in which the two atoms 
of hydrogen are replaced by two ethyl groups, is formed when 
silver sulphate is warmed with ethyl iodide ; double decom- 
position takes place, thus : 

Ag^SO* + 2C^H^I = (C^ff)^SO* 4- 2AgI 

It is an oily liquid having an acrid taste. Its density is 
1.184. It boils at 208°, with partial decomposition. 

ETHYLSULPHONIC ACID AND ETHYL 
SULPHITE. 

When mercaptan, C^H^SH, is oxidized by nitric acid, a 
thick, very acid liquid is obtained, which in a vacuum solidifies 
to a crystalline mass. It is ethylsulphonic acid, which con- 
centrated nitric acid oxidizes and converts into ethylsulphuric 
acid. Unlike the latter, ethylsulphonic acid is very stable. 
It is not decomposed by boiling with potassium hydrate : when 
fused with the latter, it yields potassium sulphite and alcohol. 

C^ff .SO'K + KOH = C^H^OH + K^SO^ 

Phosphorus pentachloride converts it into ethylsulphonic 
chloride, C^H^-SOICI, a Hquid boiling at 173°. 

Ethylsulphonic acid is analogous in its properties and con- 
stitution to phenylsulphonic acid, and its analogues, which 
will be described farther on. Ethylsulphonic acid is the sul- 
phonic derivative of ethane. 

C2H6 ethane. C^B.^ benzene. 

C2H5.S03H ethylsulphonic acid. C6H5.S03H phenylsulphonic acid. 

The sulphonic acids may be considered as derivatives of 
a hypothetical acid, H.SO^OH, to which the name unsym- 
metrical sulphurous acid has been given. The hydrogen atom 
in direct combination with the sulphur is replaceable by ethyl, 



ETHYL SULPHITES. 513 

phenyl, etc., and the sulphonates result from the replacement 
of the remaining hydrogen by metals or alcohol radicals. 

There is possible another sulphurous acid, symmetrical sul- 
phurous acid HO.SO.OH, and derivatives of this acid are 
also known : they are the sulphites of the alcohol radicals, 
and present the structure SO(OE,)^. 

1. If silver sulphite and ethyl iodide be heated together, 

a double decomposition takes place, yielding silver iodide and 

ethyl sulphonate. 

AgS02.0Ag + 2C2H5I = 2AgI + C2H5.S02.0C2H5 
Silver sulphite. Ethyl iodide. Ethyl sulphonate. 

This is the ether of the ethylsulphonic acid which has 
been described. It may be obtained by the action of ethyl- 
sulphonic chloride on sodium ethylate. 

C2H5.S02.C1 + C2H5.0Na = NaCl + C2H5.S02.0C2H5 

It is a liquid, boiling at 208°, and having at 0° a density 
of 1.47. 

2. By the action of thionyl (sulphuryl) chloride on absolute 
alcohol, ethyl sulphite is obtained isomeric with the preceding. 

SO<g} + 2C2H5.0H = 2HC1 + SO<^gg 
Thionyl chloride. Symmetric ethyl sulphite. 

This ether corresponds to ethyl sulphate. When heated 
with water it is decomposed into sulphurous acid and alcohol. 
Phosphorus pentachloride converts it into ethylsulpliurous 
chloride, boiling at 122°. 

^^<OC2H5 + P^l' = P^^l' + C'H'^^ + S^<OC2H5 

Ethyl sulphite. Ethylsulphurous chloride. 

When it is treated with an equivalent quantity of potas- 
sium hydroxide in alcoholic solution, potassium ethylsulphite 
separates in brilliant scales. 

We have, therefore, two distinct series of compounds, viz. : 



S'vO<« 




Thionyl chloride. 




so<oS 


Svi02<Hj 


Sulphurous acid (unknown). 


Unsymmetrical sulphurous acid (unknown). 


^^<OC2H5 


S0Kc2H» 


Potassium ethylsulphite. 


Ethylsulphonic acid. 


SO<Q(32H5 


.^2^0C2H5 
S0'<C2H5 


Ethyl sulphite. 


Ethyl sulphonate. 


hh 





514 ELEMENTS OF MODERN CHEMISTRY. 



PHOSPHORIC ETHERS. 

Orthophosphoric acid forms three ethyl ethers, and in general 
three series of ethers corresponding to the three series of ortho- 
phosphates. 
PO(OH)\OC'H0 PO(OH)(OC^H5)3 PO(OC^H^y 

Monethylpliosphoric acid. Diethylphosphoric acid. Triethylphosphate. 

We can only describe triethylphosphate, which may be ob- 
tained by the action of anhydrous ether on phosphoric anhy- 
dride, or by the action of phosphorus oxy chloride on sodium 
ethylate. 

POCF + SC^H^ONa = 3NaCl -f PO(OC^H^)^ 

De Clermont has obtained it by the reaction of ethyl iodide 
with silver phosphate. 

It is a syrupy liquid, soluble in water, alcohol and ether. 
Its density at 12° is 1.072. It boils at 215°. It is readily 
decomposed by water into alcohol and diethylphosphoric acid. 

POCOC^^H^y + H^O = PO<^(^,jj5)2 + C^H^OH 

NORMAL ETHYL BORATE. 

Triethyl borate, corresponding to boron trichloride, BCP, is 
obtained by distilling borax with potassium ethylsulphate. It 
is also formed, independently of other boric ethers, by the 
action of boron trichloride on absolute alcohol. It is a color- 
less, limpid liquid, boiling at 119°. Density, 0.885. It burns 
with a green flame. Water decomposes it into boric acid and 
alcohol. 

ETHYL SILICATES. 

Ebelmen has described several silicates of ethyl. To siHcon 
tetrachloride, SiCl*, there corresponds an ortho-silicic ether, 
Si(OC^H^)* ; to the chloride, Si^CP, there corresponds an ether, 
Si^(OC^H5)6. A metasilicic ether, SiOCOC^HS)^ has also been 
described, but its existence is not certainly established. 

Ethyl orthosilicate, Si(OC^H^)*, is a colorless liquid, boiling 
at 165-168°, and having a density of 0.933. It burns with 
a brilliant white light, diffusing a smoke of silicic acid. It is 
insoluble in water, which gradually decomposes it into alcohol 



ETHYL ORTHOCARBONATE. 515 

and silicic acid, the latter being deposited as a very hard, 
vitreous mass. 

Ethyl disilicate, Si^(OC^H^)^, is formed by the action of 
silicon chloride on alcohol not absolutely free from water. 

ETHYL OETHOCARBONATE. 

C(OC2H5)* 

Basset obtained this ether by causing sodium ethylate to 
react with chloropicrin. 

C(NO^)CP + 4C^H^0Na = NaNO^ + 3NaCl + CCOC^H^* 

Chloropicrin. Sodium ethylate. Sodium nitrite. Ethyl orthocarbonate. 

It is an ethereal liquid, boiling at 158-159°. Its conversion 
into guanidine by the action of ammonia has already been 
indicated (page 473). 

Ethyl orthocarbonate corresponds to an unknown ortho- 
carbonic acid which would be derived from carbon tetrachloride. 
CCl* C(OH/ C(OG'Wy 

ETHYL CARBONATE. 

C2H5 I „^3 C2H5.0\^^ 

Ettling obtained this compound by introducing potassium or 
sodium little by little into ethyl oxalate heated to 130°. The 
metal dissolves, disengaging carbon monoxide. A brown mass 
is obtained, which must be distilled with water. The ethyl car- 
bonate which passes over is dehydrated with calcium chloride 
and distilled. 

It may also be obtained by double decomposition by heating 
ethyl iodide with silver carbonate (P. de Clermont), or by the 
action of ethylchlorocarbonate (page 516) on sodium ethylate. 

^^< WH^ + C^mONa = C0<g^'^5 + NaCl. 

Ethyl carbonate is a colorless liquid, having a pleasant, 
ethereal odor ; its density at 0° is 0.9998, and it boils at 125°. 
In the cold, ammonia converts it into ethi/I carbamate, or 
urethane, a body soluble in water and alcohol, and crystallizable 
in large tables fusible at 51-52°, and boiling at 180° (Dumas). 

C2H5;o>CO + NH3 = c2h5)>CO + C'HS.OH 
Ethyl carbonate. Ethyl carbamate. 



516 ELEMENTS OP MODERN CHEMISTRY. 

It yields urea and alcohol when heated to 100° with am- 
monia. 

C2H5:o>^^ + 2NH3 = C0<™ + 2C2H5.0H 

Ethyl carbonate. Urea. 

ETHYL CHLOROCARBONATE. 

CL 



C2H50 



>co 



Dumas obtained this ether by passing carbonyl chloride 
into alcohol. Water is added to the product of the reaction, 
and the insoluble liquid is separated, dried, and distilled. 

^J>CO + C2H5.0H ^ HCl + C2H50>^^ 
Carbonyl chloride. Ethyl chlorocarbonate. 

It is a liquid having a pungent, ethereal odor. It boils at 
94°. Hot water decomposes it. Ammonia converts it into 
ethyl carbamate, or urethane. 

C2H5S>CO + 2NH3 = NH^Cl + C2HH)>C0 

ETHYL ISOCYANATE. 

C2H5-N:=CO 

This compound is prepared by distilling on an oil-bath a 
mixture of 2 parts of potassium ethylsulphate and 1 part of 
recently-prepared and well-dried potassium isocyanate. The 
product which condenses in the receiver is rectified on a water- 
bath (Wurtz). Ethyl isocyanate is a colorless liquid, having a 
very irritating odor. It boils at 60°. Potassium hydrate de- 
composes it into carbonic acid gas and ethylamine. It com- 
bines with ammonia, developing heat and producing ethylurea 
(page 481). 

The bodies which were formerly known as cyanic acid and 
ethyl cyanate, are only isomerides of the oxygen compounds 
of cyanogen. They have been described as isocyanic acid 
and isocyanate of ethyl. The true cyanic ether, (C^H^O)CN, 
or rather a polymeride of that body, has been obtained by 
Cloez. It is formed by the action of cyanogen chloride on 
ethylate of sodium. 

CNCl -f Na.OC^H^ = CN.OC^H^ + NaCl 

Cyanogen chloride. Sodium ethylate. Ethyl <>yauate. 

Potassium hydroxide decomposes the true ethyl cyanate, like 



SATURATED HYDROCARBONS. 517 

all other compound ethers, into alcohol and the corresponding 
potassium salt (cyanate), or into the decomposition products of 
that body, — carbon dioxide and ammonia. 

CYANURIC ETHEKS. 

When potassium isocyanate is distilled with ethyl sulphate, 
besides the ethyl isocyanate which has just been described, there 
is formed also the isocyanurate. 

C'OW (C'H^)=^ = (CO)^=(N.C2H0' 
The latter condenses in a solid white mass which may be 
purified by recrystallizatioa from boiling alcohol. It crystallizes 
in brilliant prisms, fusible at 95° ; it boils at 276° (A. Wurtz). 
Boiling potassium hydroxide decomposes it, like the isocyanate, 
with disengagement of carbon dioxide, a reaction which justi- 
fies the constitution indicated by the preceding formula. 

Its isomeride C^N^(OC^H^)^, which corresponds to the nor- 
mal cyanuric acid (page 474), melts at 29° and boils at 275°. 

The mother liquor from which triethyl isocyanurate has 
deposited, contains diethyl isocyanurate, C^O^N^H(C'^II^)^, 
which crystallizes in six-sided prisms, fusible at 173°. 

Normal methyl cyanur ate is formed by the action of cyanogen 
chloride on sodium methylate. 

3CNC1 + SCHlONa = 3NaCl + C^N^(OCH^)' 

It crystallizes in needles fusible at 132°. It boils between 
160 and 170°, and at this temperature is converted into its 
isomeride methyl isocyanurate, fusible at 175°, and boiling at 
296°. By the action of boiling potassium hydroxide, it is 
decomposed into potassium cyanurate and methyl alcohol. 

SERIES OF SATURATED HYDROCARBONS. 

To methane and ethane, which have already been described, 
are related numerous hydrocarbons belonging to the same 
series, CH^''"^^. They are called saturated because no hydro- 
carbons are known in which the number of hydrogen atoms 
exceeds that indicated by the preceding formula. Again, the 
hydrocarbons in question can fix directly no other atoms. For 
example, in order that chlorine can enter into one of their 
molecules, hydrogen must first be removed, and this displace- 

44 



518 ELEMENTS OP MODERN CHEMISTRY. 

ment is known to take place, atom for atom, according to the 
law of substitution. Thus, if chlorine be made to act upon 
the hydrocarbon C^H^* (hexane), the compounds C^H^^Cl, 
C^H^^CP, C*^H^^CP, may be obtained successively. Let us con-< 
sider the first of these compounds, C^H^^Cl. The CI may be 
replaced by the group OH, and the chloride is thus converted 
into an alcohol. For this purpose the chloride is caused to 
react with a silver salt, the acetate, for example, and hexyl 
acetate is formed by double decomposition. 
C'Hi^Cl + AgC^ffO^ = C^H^lC^ffO^ + AgCl 

Hexlyl chloride. Silver acetate. Hexyl acetate. 

Boiling potassium hydroxide will transform this ether into 
hexyl hydroxide. 

C^H^^C^H^O^ + KOH = KO^H^O'^ + C^H^IOH 

Hexyl acetate. Potassium acetate. Hexyl hydroxide. 

This series of reactions permits of the successive transforma- 
tion of any hydrocarbon of the saturated series into a chloride, 
an acetate, and a hydroxide, and the latter is the alcohol corre- 
sponding to the hydrocarbon. The following is the series of 
saturated hydrocarbons : 



CH4 


methane. 


C2H6 


ethane. 


C3H8 


propane. 


C4H10 


butanes. 


C5H12 


pentanes. 


C6H14 


hexanes. 


Cmi6 


heptanes. 


C8H18 


octanes. 


C9H20 


nonanes. 


C101P2 decanes, etc. 



All of these hydrocarbons, after the fourth of the series, up 
to the term C^'^H^*, have been obtained from petroleum and 
the products of distillation of bitumen and peat. Towards 
the close of the distillation, when the temperature passes above 
300°, the products which distil condense to a solid mass on 
cooling. When properly purified, this solid forms a colorless, 
translucent mass, which has received the name paraffin. It 
is probably a mixture of several hydrocarbons of the series 
Qnjj2ii+2_ j^g point of fusion varies between 45 and 65°. 

All of the compounds belonging to this series cannot be 
described here, but we may briefly consider their constitution. 

The third member of the series, propane, C^H^, has the con- 
stitution indicated by the formula CH^-CH^-CHl It is a gas 
which liquefies at — 1*7°. 



PETROLEUM. 519 

Its higher homologue, butane, C*H^°, has the constitution 
CH'-CH'-CH'-CH^ and can be obtained by the action of 
zinc or sodium on ethyl iodide. 

2C'^H^I + Na^ = 2NaI + C'W 

It is a colorless gas, condensable at +1°. But we have 
here a remarkable instance of isomerism. There is another 
butane, isomeric with the preceding, and having the consti- 

QJJ3 

tution expressed by the formula CH^-CH<<pTj3' It is tri- 

methyl-methane, CH(CH^)^, while normal butane is dimethyl- 
ethane, C^H*(CH^)^ or propyl-methane, CH^(C=^H^}. The sig- 
nification of these words and formulae is evident. Trimethyl- 
methane is methane, CH*, in which three atoms of hydrogen 
are replaced by three methyl groups. The difi'erence in the 
atomic grouping is attended by a difi'erence in properties. 
Trimethyl-methane is a gas which condenses only at — 17°. 

The succeeding terms of the series present isomerisms of 
the same kind, but much more numerous as their molecular 
complication is greater. They need not be described here, since 
the same general principles apply to all. 

PETROLEUM. 

Petroleum, or rock oil, was known to the ancients, oil-springs 
existing in Persia, India, Italy and Russia. It was used by 
the American Indians, but until 1859 mineral oil was obtained 
only in small quantities, usually by the distillation of argil- 
laceous rocks saturated with hydrocarbons, such as boghead 
coal. In 1859 the discovery of numerous and prolific oil- 
bearing soils in Northwestern Pennsylvania led to the method 
now employed of sinking deep wells, from which the oil either 
flows naturally, by reason of interior pressure, or is pumped by 
machinery. A single well has furnished two thousand barrels 
of oil a day. 

Crude petroleum is usually dark brown in color, often 
having a greenish reflection. It is sometimes mobile, some- 
times viscous like molasses. Its density varies from 0.75 to 
0.92. By fractional distillation it can be separated into a large 
number of hydrocarbons, most of which are homologues of 
marsh gas. Schorlemmer, and Pelouze and Cahours, have thus 
succeeded in isolating from petroleum the whole saturated series 
from C*H^° to C^^H^*. American petroleum consists almost 



520 ELEMENTS OF MODERN CHEMISTRY. 

entirely of hydrocarbons of tlie series C'^H^'' + ^, while Eussian 
petroleum contains considerable quantities of the naphthenes, 
a series of hydrocarbons related to benzene. 

For commercial purposes the crude oil is subjected to frac- 
tional distillation ; that is, it is heated, and the fractions pass- 
ing over at different temperatures are collected separately. 
Under such circumstances, American petroleum at 70° gives 
off the volatile hydrocarbons, which constitute 'petroleum 
ether ; gasoline distils between 70° and 90°, and the portion 
passing between 90° and 150° is known as henzine. Above 
150°, and up to about 300°, refined petroleum, or kerosene, is 
collected. From the latter temperature up to 400° heavy 
oils of a density from 0.83 to 0.9, and valuable as lubricants, 
are obtained. Much paraffine distils towards the end of the 
operation, and a residue of coke remains in the retort. 

Petroleum ether having a density of about 0.60 is used for 
the artificial production of cold, and as a solvent for fatty 
matters, and gasoline having a density of 0.63 serves for the 
manufacture of an illuminating gas. Benzine, which must 
not be confounded with benzene (page 671), is largely em- 
ployed on account of its solvent powers for resins, fats, oils, 
etc., especially in cleaning and scouring. 

Kerosene, or illuminating oil, should contain no product 
whose boiling point is below 150°. The comparative safety of 
the oil is usually determined by slowly heating it, and observing 
by means of a thermometer the temperature at which it 
emits inflammable vapors, and that at which the oil itself 
ignites. A lighted match is passed over the surface of the 
warm oil until the flashing point and igniting point are attained. 
The former should not be below 60°, and the latter not lower 
than 65.5°. 

SERIES OF ALCOHOLS. 

Ethyl alcohol, of which the more important compounds 
have been briefly described, is not the only product of the fer- 
mentation of saccharine liquids. Other alcohols are formed in 
small quantity in this reaction, which is conducted on an exten- 
sive scale in the arts. Among these alcohols of fermentation 
are the following : 

Propyl alcohol, or propyl hydroxide, C^H'^.OH 
Butyl alcohol, or butyl hydroxide, C^H^.OH 
Amyl alcohol, or amyl hydroxide, C^Hii.OH 
Hexyl alcohol, or hexyl hydroxide, C^H^^.OH 
Heptyl alcohol, or heptyl hydroxide, C^Hi^.QH 



SERIES OF ALCOHOLS. 521 

To each of these alcohols correspond numerous ethereal com- 
pounds in which the groups propyl, C^H^, hutyl, C*H^, amyl, 
C^H^^, etc., are substituted for the hydrogen of the hydj'acids 
and oxyacids. To each of these alcohols correspond also an 
aldehyde and an acid, just as ordinary aldehyde and acetic acid 
correspond to ordinary alcohol or ethyl hydroxide. 
CH3 CH3 CH3 

CH2.0H CHO CO.OH 

Alcohol. Aldehyde. Acetic acid. 

CH2-CH3 CH2-CH3 CH2-CH3 

CH2.0H CHO CO.OH 

Propyl alcohol. Propaldehyde. Propionic acid. 

C3H7 C3H7 C3H7 

CH20H CHO CO.OH 

Butyl alcohol. Butaldehyde. Butyric acid. 

All of these alcohols contain a group CH^OH united to a 
group or radical, C"H^''+\ When they are converted by oxi- 
dation into aldehydes and acids, the group CHI OH is trans- 
formed into a group CHO, characteristic of the aldehydes, or 
a group CO.OH, characteristic of the acids. These alcohols 
are said to be primary. Beginning with butyl alcohol, the 
primary alcohols may have several isomeric modifications, as 
will be seen shortly. Independently of the primary alcohols, 
there are others, isomeric with the preceding, but distinguished 
from them by the fact that they do not yield corresponding 
aldehydes and acids when oxidized. These iso-alcoliols are 
divided into secondary^ which contain the group CH.OH, and 
tertiary^ which contain the group C.OH (Kolbe). Without 
entering into the details of this subject, we may cite two 
examples : 

1. By the action of nascent hydrogen acetone yields second- 
ary propyl alcohol, which oxidation reconverts into acetone. 
CH3 CH3 CH3 CH3 



CO + H2 = CH.OH 


CH.OH + = H20 + CO 


CH3 CH3 

Acetone. Isopropyl alcohol. 


CH3 CH3 



2. Butlerow discovered an isomeride of butyl alcohol, and 
named it tertiary hutyl alcohol ; its constitution is thus ex- 
pressed : 

CH3 

CH3-C.0H 
CH3 
44* 



522 ELEMENTS OF MODERN CHEMISTRY. 

This alcohol contains, as is seen, the group C.OH. It yields 
neither aldehyde nor acid by oxidation. 

In the primary alcohols, the OH is united to a C which is 
combined with only one other carbon atom ; in the secondary 
alcohols, to a C united to two other carbon atoms ; while in 
the tertiary alcohols, the C to which the hydroxyl is attached 
is joined to three other atoms of carbon. 

In order to exactly designate the class of any alcohol by 
its name, Kolbe proposed to consider all alcohols as derived 
from methyl alcohol, which he named carhinol. The replace- 
ment of one of the hydrogen atoms in the CH^ group by a 
hydrocarbon radical would yield a mono-substituted carbinol 
or primary alcohol ; the disubstituted carbinols are secondary 
alcohols, while the tertiary alcohols are trisubstituted carbi- 
nols. This may be more clearly understood by the aid of 
the following formula : 

(C2H5)CH'^.OH (C2H5)2CH.OH {QWfQ.OB. 

Ethyl carbinol. Diethyl carbinol. Trimethyl carbinol. 

Primary propyl alcohol. Secondary (iso) amyl alcohol. Tertiary butyl alcohol. 

PROPYL ALCOHOLS. 

Kormal Propyl Alcohol.— CIP-Cff-CHlOH.— This was 

discovered by Chancel in the oily liquid remaining after the 
distillation of brandy. It is a spirituous liquid, boiling at 98°. 
Its iodide, O^H^I, boils at 104.5°. 

Isopropyl Alcohol, CH^-CH.OH-CH^, is prepared by the 
action of sodium amalgam upon acetone in aqueous solution, 
according to the reaction given on the previous page. 

It boils at 81°. When propylene gas is heated with hydri- 
odic acid, isopropyl iodide, C^H^I, is obtained, boiling at 92°. 
C^H^ + HI = C^H^I 

Propylene. Isopropyl iodide. 

BUTYL ALCOHOLS. 

C*HioO 
There are four butyl alcohols. The best known is the 
Butyl Alcohol of Fermentation, or isopropylcarbinol. 
In 1852, Wurtz obtained it from the fusel-oil from the rec- 
tification of beet-root alcohol. It is a colorless liquid, having 
a penetrating odor analogous to that of amyl alcohol, but more 
spirituous. It dissolves in 10.5 times its volume of water. It 



SERIES OP ALCOHOLS. 523 

boils at 109°, and yields on oxidation an acid isomeric with 

butyric acid and called isohutyric. Its density at 18° is 0.805. 

It may be regarded as ordinary alcohol in which two atoms 

of hydrogen are replaced by two methyl groups. 

CH3 CH(CH3)2 

CH2.0H CH2.0H 

Alcohol. Isobutyl alcohol. 

Normal Butyl Alcohol is isomeric with the alcohol of fer- 
mentation, and by oxidation yields butyric aldehyde and butyric 
acid. Lieben obtained this alcohol by the action of sodium 
amalgam in presence of water on butaldehyde. 

C3H7 „ C3H7 

I + H2 = I 

CHO CH2.0II 

Butaldehyde, Normal butyl alcohol. 

Normal butyl alcohol is a liquid having a pleasant odor. It 
boils at 117°. Its density at 0° is 0.824. 

Fitz has obtained this alcohol, as well as ethyl alcohol and 
normal propyl alcohol, by the decomposition of glycerol under 
the influence of a peculiar organized ferment. 

Secondary Butyl Alcohol was obtained by De Luynes by 
the reduction of erythritol (page 633). This alcohol is second- 
ary, having the constitution CH^-CH2-CH(0H)-CH^ It 
boils at 98-100°. Density at 0°, 0.85. The corresponding 
iodide, CH^-Cff-CHI-CH^ boils at 118°. It is formed by 
the following reaction : 
C^tpoO* + 7HI = Q^Wl -f 4H20 + 3P 

Erythritol. Secondary butyl iodide. 

Tertiary Butyl Alcohol, discovered by Butlerow, has re- 
ceived the name trimetliylcarhinol^ on account of its constitution, 
which has already been indicated. It is a compound crystal- 
lizing in right-rhombic prisms, melting at 23°. It boils at 
83-84°, and is soluble in all proportions of water. 

In conclusion, four alcohols are known having the composi- 
tion C'^H^°0, and presenting a remarkable instance of isomer- 
ism. Their constitutions are again indicated in the following 
formulae : 



CH3 


CH3 


CH3 


CH3 


CH2 


CH3-CH 


CH2 


CH3-C.0H 


CH2 


CH2.0H 


CH.OH 


CH3 


CH2.0H 

Normal primary 

butyl alcohol. 

(Lieben.) 


Primary isobutyl 

alcohol (fermentation). 

(Wurtz.) 


CH3 
Secondary butyl 
alcohol. 
(De Luynes.) 


Tertiary butyl 

alcohol. 

(Boutlerow.) 



524 ELEMENTS OF MODERN CHEMISTRY. 



AMYL ALCOHOLS. 

C5H120 
Theory predicts the existence of eight isomeric amyl alcohols : 

1. Four primary alcohols which may be regarded as formed 
by the substitution of various alcoholic groups for one atom of 
hydrogen of the methyl group in methyl alcohol. 

H C-(CH3)3 CH <Q2H^5 CH2.C3H7 CH2-C3H7i 

CH2.0H CH2.0H CH2.0H CH2.0H CH2.OH 

Methyl alcohol. Tertiary- Active amyl Normal amyl Amyl alcohol of fer 

butylcarbinol. alcohol. alcohol. mentation. 

Butyl carbiuol. Isobutylcarbinol. 

2. Three secondary alcohols, in which two atoms of hydrogen 
of the methyl group in methyl alcohol are replaced by alcoholic 
groups. 

H C2H5 C3H7 cmn 

H-CH.OH C2H5-CH.OH CH^-CH.OH CH3-CH.0H 

Methyl alcohol. Diethylcarbiuol. Propylmethylcarbinol. Isopropylmethyl- 

carbinol. 

3. One tertiary alcohol, in which one ethyl group and two 
methyl groups replace the three hydrogen atoms of the CH^ 
in methyl alcohol. 

H C2H5 

H-C-OH CH3-C.0H 

I I 

H CH3 

Methyl alcohol. Dimethylethylcarbinol. 

All of these eight isomerides are actually known. 
^Normal Amyl Alcohol, CH^-CH^-CH^-CH^-CHIOH.— 

Lieben obtained this compound by the action of nascent 
hydrogen on valeral, the corresponding aldehyde. It is a 
liquid, almost insoluble in water, boiling at 137°. Its density 
at 0° is 0.829. Oxidizing agents convert it into normal 
valeric acid. 

The corresponding chloride, C^H^Cl, boils at 106-107°. It 
may be prepared by the action of hydrochloric acid upon the 
normal alcohol, and has also been obtained by the action of 
chlorine on normal pentane, CH^-(CH^)^-CH^, as described on 
page 504. 

Amyl Alcohol of Fermentation. — This consists in great 

part of inactive isobutyl carbinol, ^g3>CH-CH2-CH^OH, 
but contains also a variable quantity of active amyl alcohol. 



AMYL ALCOHOLS. 525 

It may be obtained by fractional distillation of the fusel oil 
from beet-root and potatoes, as well as of that from the marc 
of grapes, whiskey, etc. These products are only the residues 
of the distillation of alcohol from various sources. The 
inactive amy! alcohol or isobutylcarbinol may be separated by 
the following process, indicated by Pasteur. 

By treatment with sulphuric acid the crude amyl alcohol is 
converted into amylsulphuric acid. The liquid is diluted with 
water, neutralized with barium carbonate, and filtered. Two 
barium amylsulphates are thus obtained, of which the one is 
less soluble than the other, and crystallizes first when the solu- 
tion is evaporated, while the other remains in the mother 
liquid. The former is derived from the inactive alcohol, the 
latter from the active alcohol ; these alcohols are obtained by 
decomposing the corresponding barium salts with sulphuric acid, 
filtering, and distilling with water the free amylsulphuric acids. 

SO^<^g + H^O = S0X0H)2 + C^H".OH 

Amylsulphuric acids. Sulphuric acid. Amyl alcohols. 

Isobutylcarbinol has been obtained by synthesis, and the 
process clearly proves its constitution (Balbiano). The con- 
stitution of butyl alcohol of fermentation has been established 
with certainty by Erlenmeyer. This alcohol may be converted 
successively into iodide and cyanide, and this, by decomposition 
with potassium hydrate, into inactive valeric acid. The barium 
salt of the latter acid when distilled with calcium formate 
yields the corresponding aldehyde, valeraldehyde (Piria), and 
this is converted into inactive amyl alcohol by the action of 
nascent hydrogen. 

QH3>CH-CH^-CH0 + H^ == ^g3>CH-CH^-CH2.0H 

Valeraldehyde. Isobutylcarbinol. 

Properties. — Pure isobutylcarbinol is a colorless, somewhat 
oily liquid, soluble in fifty parts of water at 13°. Its density 
at 0° is 0.823, and it boils at 131.4°. When oxidized it 
yields inactive valeraldehyde and acid. 

C^Hi^O 4- = H^O + c^ir°o 

Amyl alcohol. Valeric aldehyde (valeral). 

C^H^^O + 0' = H^O + C^H^oQ^ 

Valeric acid. 

The crude alcohol of fermentation is an oily liquid, of a dis- 
agreeable odor. It boils at 129-132°. It turns the plane of 



526 ELEMENTS OF MODERN CHEMISTRY. 

polarized light to the left, but its rotatory power is variable, 
for it contains variable proportions of active amyl alcohol. 

When distilled with zinc chloride, it yields ordinary amylene, 
which is a mixture of several isomeric amylenes, trimethyl- 
ethylene being the most abundant. 

Amyl alcohol. Amylenes. 

Many amyl derivatives have been studied. They resemble 
the ethyl compounds, but contain, of course, the group C^H^^ 
instead of C'H^ 

Amyl oxide, r(5oii!>0, is formed, together with amylene, 

by the action of sulphuric acid on crude amyl alcohol (William- 
son). It is a colorless liquid, of an aromatic odor, boiling at 
176°. 

Amyl chloride, C^H"C1, is a colorless liquid, boiling at 
101.4°. Amyl bromide, C^H"Br, boils at 120.4°. Amyl 
iodide, C^H^^I, is prepared by a process similar to that which 
yields ethyl iodide. It is a colorless liquid, boiling at 148°. 
It turns brown on exposure to the light. 

Amyl nitrite, C^H^NO^ is prepared by passing nitrous 
vapors, made by the action of nitric acid on starch, into amyl 
alcohol, and distilling the carefully washed product. It is a 
pale yellow liquid, boiling at 96°, and having a peculiar odor 
somewhat like that of apples. Its vapor when inhaled pro- 
duces dilatation of the capillary system, and violent but tran- 
sitory headache. Its inhalation has been recommended as a 
remedy for sea-sickness, in certain heart-affections, and as an 
antidote in cases of poisoning by chloroform vapor. 

Active Amyl Alcohol is contained to the extent of about 
thirteen per cent, in crude amyl alcohol. One method of 
separation has already been indicated, but Le Bel has proposed 
a better method when it is desired to prepare only the active 
alcohol. If hydrochloric acid gas be passed through the crude 
alcohol, the inactive alcohol is first attacked and converted into 
chloride ; the active alcohol then remains after the separation 
of the inactive chloride. 

It boils at 127°. It rotates the plane of polarized light to 
the left [a]D = —4.4°. Its chloride boils at 97-99° ; its iodide 
at 144-145°. Oxidation converts it into active valeric acid ; 

hence its constitution is probably p2tr6>C!H-CH^OH. 



HIGHER ALCOHOLS. 527 

Tertiary Amyl Alcohol, or Hydrate of Amylene. This 
alcohol is prepared by treating with hydriodic acid trimethyl- 
ethylene, described on page 574, which forms the greater part 
of crude amylene. 

^^3>C=:CH-CH3 + HI = ^|3>CI-CH^-Cff 

Trimethylethylene. Trimethylethyl iodide. 

The iodide so formed, when acted on by water and silver 
oxide, yields the corresponding hydrate, which is tertiary amyl 
alcohol or dimethylethylcarbinol. 

It is a mobile, colorless liquid, having an odor somewhat like 
camphor. At — 12° it forms a crystalline mass ; it boils at 
102.5°, and at 200° is decomposed into amylene and water. 
By reason of the latter reaction, Wurtz, who discovered th-e 
alcohol, named it hydrate of amylene. 

Its chloride boils at 86°, its bromide at 108-109°, and its 
iodide at 127-128°. 

Oxidation converts it into acetic acid and acetone. 



HIGHER ALCOHOLS. 

Of th.e rapidly increasing number of members of this series 
which are becoming well known, we can consider but a few. 

Hexyl and Heptyl Alcohols. — Faget announced that the 
residues from the distillation of fusel-oil from fermented 
grape-juice contained a small quantity of liexyl (C^H^^O) and 
liepyl (C^H^^O) alcohols, but the existence of such alcohols 
in that product has not been corroborated. 

Normal hexyl alcohol has been obtained from the volatile 
oil of the seeds of Heracleum gigantenm^ an oil which contains 
butyrate of hexyl, C^H^lC^H^Ol The normal alcohol boils 
at 157-158°. 

K'ormal heptyl alcohol, C^H^^O, has been prepared by the 
action of nascent hydrogen on oenanthic aldehyde C^H^^O. 
It boils at 175-177°, and has an aromatic odor. 

Octyl Alcohols, C^H^^O.- -Normal octyl alcohol may be ex- 
tracted from the seeds of Heracleum spondylium and Hera- 
cleum giganteum^ in which octyl acetate, C^H^^C^H^O^, exists. 
This ether is separated and decomposed by boiling potassium 
hydroxide. Its boiling-point is 199°. 

Bouis discovered secondary octyl alcohol. By boiling one 



528 ELEMENTS OF MODERN CHEMISTRY. 

of the acids produced by the saponification of castor-oil, rici- 
nolic acid, with potassium hydroxide, he succeeded in obtaining 
sebacic acid and a new secondary alcohol. This is octyl alco- 
hol, C^H^^O, a colorless liquid having a pleasant, aromatic odor, 
and boiling at 178°. The following equation explains its 
formation : 

Qi8H3*0^ + 2K0H = WC'WO' + C^H^^O -f H^ 

Kicinolic acid. Potassium sebacate. Octyl hydroxide. 

Cetyl Alcohol. — The solid portion of an oil which fills 
the cranial sinuses of the sperm-whale is called spermaceti. 
When properly purified it occurs in beautiful pearly plates, 
fusible at 49°. It is a compound ether of which the nature 
was recognized by Chevreul in 1823. By submitting it to the 
action of potassium hydroxide, that chemist decomposed it 
into palmitic acid and a new alcohol which he called ethal, to 
denote its relations with alcohol and ether. It is now called 
cefi/l alcohol, or ceti/l hydroxide. 

^cSh33>^ + ^^^ = C16H33.0H + KC16H3102 
Cetyl palmitate. Cetyl hydroxide. Potassium palmitate. 

It belongs to the same homologous series as the preceding 
alcohols. 

Alcohols from Wax. — The most complex alcohols of the 
series under consideration were obtained from wax by Brodie. 
Ordinary beeswax is a mixture of a fatty acid, C^^H^^O^ called 
cerotic acid (cerin), and a compound ether, the pahyittate of 
rtiyricyl (myricin). The two bodies are separated by alcohol, 
which readily dissolves the first, but in which the second is but 
slightly soluble. By boiling the palmitate of myricyl with 
potassium hydroxide, it breaks up into palmitic acid and 
hydroxide of myricyl, or myricyl alcohol, C^°H^'^0. 

Chinese wax is a compound ether; it is cerotate of ceryl, 
and may be decomposed by caustic potash into cerotic acid and 
ceryl hydroxide, or ceryl alcohol, C"H^^O. The hydroxides of 
cetyl and ceryl are solid bodies. 

ALLYL ALCOHOL. 

C^H^.OH = CH2^CH-CH2.0H 

All the alcohols thus far considered belong to the series 
(^njj2n+2Q There are other monohydric alcohols which belong 
to different series, that is, in which there are different relations 



ALLYL ALCOHOL. 529 

between the number of hydrogen atoms and the number of 
carbon atoms. Among these other alcohols, the most impor- 
tant is allyl alcohol^ or hydroxide of allyl^ so named because it 
is closely related to the essential oil of garlic, which is allyl 
sulphide. Another natural oil, that of mustard, is sulpho- 
cyanate of allyl. 

C^^H^.OH (C^H5)2S C^H^CNS 

Allyl hydroxide. Allyl sulphide. Allyl sulphocyanate. 

Hofmann and Cahours prepared allyl hydroxide and a great 
number of its derivatives artificially by the aid of allyliodide^ 
C^HP, which is formed when glycerol is acted upon by iodide 
of phosphorus, P"''!* (Bertheiot and de Luca). This iodide, 
whose relations to allyl alcohol are the same as those of ethyl 
iodide to ordinary alcohol, is a colorless liquid, having a slightly 
pungent, garlicky odor, and boiling at 101°. 

When heated with mercury and concentrated hydrochloric 
acid, it yields pure propylene gas (Bertheiot). 

2C^H^I -f 2HC1 + 4Hg = 2C^H*' + HgT + Hg^CP 

Allyl iodide. Propylene. 

ToUens and Henninger discovered a very simple process for 
the preparation of allyl alcohol. It consists in heating formic 
acid, or oxalic acid, from which the former acid is produced, 
with glycerol to 220°. The allyl alcohol which distils is 
washed with a concentrated solution of potassium carbonate, 
and rectified over lime. In this reaction, a monoformine of 
glycerol is first produced, and this decomposes at 220° into 
carbon dioxide, water, and allyl alcohol. 

fO.CHO 
C3H5 \ OH = C02 + H20 + C3H5.0H 
(OH 

Monoformine of glycerol. Allyl alcohol. 

It will be seen that the reaction is really a reduction. 

Allyl alcohol is a colorless liquid, boiling at 97°, and having 
a pungent, alcoholic odor. It dissolves in all proportions of 
water. Density at 0°, 0.858. Allyl alcohol is an unsaturated 
compound ; it can fix directly two atoms of hydrogen, so form- 
ing normal propyl alcohol. It combines directly with bromine, 
forming dibromopropylalcohol. CH^Br-CHBr-CH^OH. 

Acrolein^ or acraldehyde, CH^ = CH-CHO, a volatile liquid 
that is formed in the distillation of fatty bodies, is the alde- 
hyde of allyl alcohol. Acrylic acid is the corresponding acid. 
X a 45 



530 



ELEMENTS OF MODERN CHEMISTRY. 



COMPOUND AMMONIAS, OK AMINES. 

Wurtz gave these names to the basic combinations resulting 
from the substitution of alcoholic radicals, such as methyl, 
ethyl, etc., for the hydrogen of ammonia. This substitution 
may be more or less complete; 1, 2, or 3 atoms of hydrogen 
may be replaced by as many alkyl groups. Hence there 
are various classes of amines ; they are designated by the names 
primary, secondary, and tertiary. 





PRIMARY AMINES. 


SECONDARY AMINES. 


TERTIARY AMINEg. 


1^1 


CH3) 


cm) 


CH3) 


H VN 


hIn 


chsIn 


ch^In 


HJ 


hJ 


HJ 


CH3J 


mmonia. 


Methylamine. 


Dimetliylamine. 


Trimethylamine. 




C2H5) 


C2H5^ 


C2H5) 




H^N 


C2H5 [ N 


C2H5 I N 




hJ 


HJ 


C2H5J 




Ethylamine. 


Dlethylamine. 


Triethylamine. 



Lastly, bases are known which are the most energetic of 
all, and may be considered as derived from the hypothetical 
hydroxide of ammonium by the substitution of alcoholic radi- 
cals for 4 atoms of hydrogen. 



N.OH 



C2H5- 
C2H5 
C2H5 
C2H5J 

Hydroxide of tetrethylammonium. 



:U 



OH 



Ammonium hydroxide. 

The latter ammoniated bases, as well as the secondary and 
tertiary amines, were discovered by Hofmann. 

The compound ammonias, or amines, are formed in the fol- 
lowing reactions : 

1. By the decomposition of an isocyanic or isocyanuric ether 

by potassium hydroxide. In this case primary amines are 

obtained (A. Wurtz). 

CO = N-C2H5 + 2K0H - NH2(C2H5) + K2C03 
Ethyl isocyanate. Ethylamine. 

2. By the action of alkyl bromides or iodides on ammonia 
(A. W. Hofmann). 



C2H5I + 
Ethyl iodide. 
2C2H5I + NH3 



zcmn 



NH3 = NH2(C2H5)HI 

Ethylamine hydriodide. 
= NH(C2H5j2HI + HI 
Dlethylamine hydriodide. 
NH3 = NH(C2H5)3HI + 2HI 
Triethylamine hydriodide. 



COMPOUND AMMONIAS. 531 

3. By decomposing carbylamines by dilute acids (Gautier). 

4. By the reduction of nitromethane and its homologues by 
nascent hydrogen (V. Meyer, see p. 494). 

5. By the action of nascent hydrogen on the alkyl cyanides, 
also called nitriles (Mendius). 

CH3.CN + H* = CH3-CH2-NH2 

Methyl cyanide, or acetonitrile. Ethylamine. 

6. By reducing oximes (p. 554) or hydrazones (p. 554) in 
alcoholic solution by means of nascent hydrogen (E. Fischer). 

General Properties. — The amines are energetic bases, pre- 
senting great analogies with ammonia, having a similar odor, 
a like solubility in water, and the same pronounced alkaline 
reaction. The more simple are combustible gases or volatile 
liquids. The basic energy increases with progressive substitu- 
tions : thus triethylamine is a stronger base than either ethyl- 
amine or ammonia, both of which it displaces from their com- 
binations. The hydroxides of the quaternary bases, or com- 
pound ammoniums, are almost as caustic as potassium hydrox- 
ide. All the compound ammonias form with platinic chloride 
crystallizable double salts comparable to ammonium chloro- 
platinate. They can replace ammonia in ammonia alum. 

When the hydrochlorides of the amines are subjected to de- 
structive distillation, they decompose into an alkyl chloride 
and a lower amine, a reaction which allows the molecules to be 
simplified by a sort of inverse substitution. 

N(CH3)4C1 = N(CH3)3 + CH3C1 

Tetramethylammonium chloride. Trimethylamine. 

N(CH3)3.HC1 = NH(CH3)2 + CH3C1 

Trimethylamine hydrochloride. Dimethylamine. 

NH(CH3)2.HC1 = NH2(CH3) + CH3C1 

Dimethylamine hydrochloride. Methylamine. 

Action of Nitrous Acid. — This acid converts primary amines 
into alcohols, water being formed and nitrogen disengaged. 

NH^CC^HO + HO.NO = C^mOH + H^O + N^ 

With the same acid the secondary amines undergo a remark- 
able reaction, giving rise to nitroso-hsises, or nitroso-Simines, 
formed by the substitution of the group nitrosyl^ NO, for the 
single atom of hydrogen in the ammonia residue NH (imidogen). 
/H /NO 

N^CH^ + NO.OH = N^CH^ + H^O 

Dimethylamine. Nitrosodimethylamine, 



532 ELEMENTS OF MODERN CHEMISTRY. 

The nitrosamines are oleaginous liquids, insoluble in water ; 
they can be distilled without decomposition, and, generally, are 
unalterable by either acids or alkalies. On the addition of 
phenol and sulphuric acid they produce intense colors. When 
their alcoholic solutions are treated with zinc and acetic acid, 
the nascent hydrogen evolved converts them into disubstituted 
hydrazines (see below). 

In the amines, nitrogen acts as a triatomic element or tri- 
valent; but it may assume two other atomicities. In sal- 
ammoniac, it is pentatomic, and it may play precisely the same 
part in the amines. 



H 


C2H5 

1 


CI 
H H 

N 


(OH)' 

(C2H5)' (C2H5)' 

N 


/\ 
H H 

Ammonia. 


C2H5 C2H5 

Triethylamine. 


H H 

Ammonium 
chloride. 


(C2H5)' (C2H5)' 

Tetrethylammonium 

hydroxide. 



Helated to the amines are various organic combinations 
which have the same constitution, but in which the nitrogen 
is replaced by an analogous element, such as phosphorus, 
arsenic, or antimony. A great number of these bodies have 
been discovered, of which the more important are 
C2H5) C2H5^ C2Hn 



C2H5 \ P'" C2H5 \ As'" C2H5 \ Sb 

C2H5J C2H5J C2H5J 

Triethylphosphine. Triethylarsine. Triethylstibine. 

Hydrazines. — The nitrogenized bases that have just been 
considered belong either to the type NX^ or to the type NX^. 
A new class of compounds has recently been discovered, be- 
longing to the type N^X^. 

It is evident that the group NH^ (amidogen) cannot exist 
in the free state. Hydrazine, discovered and described by 
Curtius, consists of two such groups, Nff-NH^ It is dia- 
mide (page 160). 

Derivatives of hydrazine, in which one or two atoms of 
hydrogen are replaced by organic radicals, had previously 
been obtained by Fischer, who described ethylhydrazine^ 
NH2-NH(C'H^), and diethylhydrazine 

N(C^H5)'-NIP 

Dimethyl- and diethylhydrazine are formed by the action 
of nascent hydrogen on the corresponding nitroso compounds 
(page 531). 



METHYLAMINE. 533 

^53>N-NO + H* = H^O + ^(C^')' 

These hydrazines are closely related to the amines by their 
chemical and physical properties. They are very volatile 
liquids, having an ammoniacal odor, and soluble in water, 
alcohol, and ether. 

METHYLAMINE. 

CH3) 
CH5N = H ^ N 

hJ 

This body may be prepared by boiling together potassium 

hydrate and methyl cyanate or cyanurate, and passing the 

vapors which are disengaged into dilute hydrochloric acid; 

methylamine hydrochloride is thus formed. 

on CH3) 

(,^^N + 2K0H = K2C03 + hIn 

Methyl cyanate. Methylamine, 

The solution is evaporated to dryness, and the residue fused 
and allowed to cool ; it is then mixed with double its weight 
of powdered quick-lime, and the mixture gently heated. The 
methylamine disengaged may be collected over mercury. 

It is a colorless gas, which condenses to a light liquid at a 
temperature a few degrees below 0°. It is inflammable, and 
burns with a pale flame. Its odor is strongly ammoniacal and, 
at the same time, recalls that of the sea. It is the most solu- 
ble of all gases. 1 volume of water at 12.5° absorbs 1153 
volumes of methylamine. The aqueous solution possesses the 
odor of the gas, a caustic taste, and a strong, alkaline reaction. 
Like ammonia, it precipitates the oxides from solutions of the 
metallic salts. 

If a solution of methylamine be added to a solution of cupric 
sulphate, a light-blue precipitate is first formed, but disappears 
if an excess of methylamine be added, yielding a beautiful blue 
solution. 

Methylamine Hydrochloride, CH^N.HCl, difi'ers from am- 
monium chloride by its solubility in boiling alcohol, from which 
it is deposited on cooling in large, colorless, deliquescent plates. 
With platinic chloride it forms a yellow precipitate, soluble in 
boiling water, from which it crystallizes in golden-yellow scales. 

It is a chhroplatinafe, (CH^N.HCniPtCh 
45* 



534 ELEMENTS OP MODERN CHEMISTRY. 



DIMETHYLAMINE, TRIMETHYLAMINE, TETRA- 
METHYLAMMONIUM HYDRATE. 

These compounds were discovered by Hofmann. 

Dimethylamine^ (CH^)^NII, is a combustible gas wliicli lique- 
fies at 8°. 

Trimethylamine^ (CH^)^N, exists ready formed in the Cheno- 
podium vidvaria, in the flowers of Cratse^us oxyacantha, in 
herring-brine, in cod-liver oil, and in coal-gas tar. Vincent 
extracts large quatities of it from the residues of the distilla- 
tion of fermented beet-juice. 

At ordinary temperatures it is a gas ; it liquefies at 9°. It is 
very soluble in water and in alcohol. It has a strong, ammoniacal 
odor, and an intense, alkaline reaction. It unites directly with 
methyl iodide, forming the iodide of tetramethylammonium. 

(CH3)^N + CH^i = (cwym 

This iodide possesses all the appearances of a salt. It is 
soluble in water, and the solution treated with silver oxide yields 
silver iodide and tetramethylammonium hydroxide. 

2(CH=^)^NI + Ag^O + H^O = 2AgI + 2(CH3)^N.OH 
The latter body is very soluble in water, and the solution is 
caustic. When submitted to dry distillation, it decomposes into 
trimethylamine and methyl alcohol. 

(CHO'N.OH = CHIOH -f (CH^)^N 

ETHYLAMINE. 
cm ) 



hJ 



Ethylamine is prepared by a process analogous to that which 
yields methylamine ; cyanate or cyanurate of ethyl is decom- 
posed with boiling potassium hydroxide, and the vapors are con- 
densed in very dilute hydrochloric acid. The dry ethylamine 
hydrochloride is then treated with quick-lime (A. Wurtz). 

Another process has been indicated by Hofmann. It consists 
in causing ammonia to react upon the bromide or iodide of 

ethyl. 

H) C2H5) 

C2H5Br + H I N = H ^ N.HBr 

hJ hJ 

Ethylamine hydrq bromide. 



DIETHYLAMINE. 535 

Ethylamine is a ligbt, mobile, colorless liquid ; it boils at 

18.7°. Its odor is strong and exactly resembles that of am- 
monia. 

Ethylamine is inflammable. It mixes with water, alcohol, 
and ether in all proportions. Its aqueous solution is caustic, 
and precipitates most of the metallic salts like solution of am- 
monia, and, like the latter, redissolves cupric hydrate, forming 
a blue liquid. 

Ethylamine Hydrochloride, C^H^N.HCl.— This salt crys- 
tallizes in large, deliquescent plates, soluble in absolute alcohol. 
Its aqueous solution yields with platinic chloride a precipitate 
composed of yellow scales, soluble in boiling water, and consti- 
tuting a chloro-platinate, (C'H^N.HCl)lPtCP. 

DIETHYLAMINE, TRIETHYLAMINE, TETKETHYL- 
AMMONIUM HYDROXIDE. 

Diethylamine, C^H^ I N, was obtained by Hofinann by heat- 
ing ethylamine with ethylbromide, and decomposing the die- 
thylamine hydrobromide formed by an alkali, 
cmn C2H5- 

.HBr 



H5) C2H5) 

H I N + C2H5Br = C2H5 I N.] 
Hj hJ 



Ethylamine. Diethylamine hydrobromide. 

The free base is a liquid having an ammoniacal odor and 
boiling at 57.5° 

Triethylamine may be formed by the action of ethyl bro- 
mide on diethylamine ; triethylamine hydrobromide is formed, 

(J2JJ5 f ]v^ jj;Bj.^ from which alkalies cause the disengagement 

of triethylamine, a colorless liquid, boiling at 91° ; its odor 
is ammoniacal and its reaction strongly alkaline. 

Tetrethylammonium Hydroxide. — When a mixture of 
ethyl iodide and triethylamine is heated on a water-bath, the 
two bodies combine, forming the compound which Hofinann 
has named tetrethylammonium iodide. 

Q'Wl -f (C^H^)^N = (C^H5)*N.I 

Ethyl iodide. Triethylamine. Tetrethylammonium iodide. 

When this is treated with silver oxide and water, it yields 
silver iodide and tetrethylammonium hydroxide, (C^H^)*N.OH, 



536 ELEMENTS OF MODERN CHEMISTRY. 

a powerful base, which is crystallizable and soluble in water. 
Its alkalinity is comparable to that of potassium hydroxide. 



ETHYLPHOSPHINES. 

Primary, secondary, and tertiary ethylphosphines are known, 
as well as the compounds of tetrethylphosphonium. 

cms] cm^-) cm^) g|n , 

Ethylphosphine. Diethylphosplaine. Triethylphospbine. Tetrethylphosphonium. 



The first two were discovered by Hofmann. The third by 
Hofmann and Cahours, who obtained it by the action of 
phosphorus trichloride on zinc ethyl. 

2PCP + 3[Zn(C^H^)^] = 2[P(C^H5y] + 3ZnCP 

Zinc ethyl. Triethylphosphine. 

The operation must be conducted out of contact with the 
air, and the zinc ethyl must be diluted with anhydrous ether. 

Monethylphosphine and diethylphosphine are produced when 
ethyl iodide is made to react upon phosphonium iodide, PH'^I, 
hydriodide of hydrogen phosphide (page 177), in presence of 
an excess of zinc oxide. 

2C2H5I + 2PH*I + ZnO = 2[(C2H5)H2P.HI] + ZnP + H20 
2C2H5I + PH^I + ZnO = (C2H5)2HP.HI + ZnF + H20 

As both reactions are accomplished simultaneously, both 
phosphines are obtained at the same time. They are separated 
by the action of water upon the two hydriodides which are 
formed. That of monethylphosphine is decomposed by water, 
while that of diethylphosphine is only decomposed by the alka- 
lies. It is sufficient then to add water to the product of the 
reaction in order to set free the monethylphosphine ; when 
the latter has been completely expelled by heat, potassium hy- 
drate added to the residue will cause the disengagement of the 
diethylphosphine. These operations should be conducted in a 
current of hydrogen. 

Monethylphosphine, (C^H^)HT. — This is a colorless liquid, 
lighter than water, in which it is insoluble, and boiling at 25°. 
It has a most disagreeable odor. It takes fire on contact with 
chlorine or nitric acid. Its hydriodide crystallizes in beautiful, 
white, quadrangular tables. 

diethylphosphine, (C^H^)'HP. — A colorless liquid, lighter 



PRODUCTS OF OXIDATION OF ETHYLPHOSPHINES. 537 

than water, and boiling at 85°. It is very avid of oxygen, and 
sometimes takes fire spontaneously on contact with the air. 

TriethyiphospMne, (C^H^)^P. — This is a colorless liquid, 
boiling at 127.5°. Density at 15°, 0.812. It combines di- 
rectly with oxygen, forming triethylphosphine oxide, (C^H^)^PO. 
The latter is a crystalline solid, very soluble in water and in 
alcohol. It distils at 240°. 

When treated with ethyl iodide, triethylphosphine yields 
tetrethylphosphonium iodide, (C^H^)*PI, a compound which 
may be obtained in beautiful crystals. When this iodide is 
acted upon by moist silver oxide, it furnishes the corresponding 
hydrate, which is an energetic base. 

2[(C'^H^)TI] + Ag^O + H^O = 2AgI + 2[(C^H^)T.0H] 

Tetrethylphosphonium Tetrethylphosphonium 

iodide. hydrate. 

PRODUCTS OF OXIDATION OF ETHYLPHOS- 
PHINES. 

When the ethylphosphines are treated with fuming nitric 
acid under suitable conditions, they act in a characteristic man- 
ner. Monethylphosphine is transformed into a dibasic acid, 
monethylpliosphinic ^ diethylphosphine yields a monobasic acid, 
dietJiylphospliinic. Triethylphosphine yields an indifferent 
oxide, which has already been mentioned. Now, if it be remem- 
bered that under the same circumstances hydrogen phosphide 
furnishes phosphoric acid, it will be seen that the preceding 
oxidation compounds may be regarded as phosphoric acid, in 



which 1, 


, 2, or 3 groups OH 


are replaced by as n 


groups. 








(■H 


rOH 




P^ H 


PQ^ OH 




1h 


[on 




Hydrogen phosphide. 


Phosphoric acid. 




rC2H5 


rc2H5 




P^ H 


PO^ OH 




U 


(OH 




Monethylphosphine. 


Monethylphosphinic acid. 




('C2H5 


rC2H5 




P^C2H5 


PO \ C2H5 




1h 


(oh 




Diethylphosphine. 


Diethylphosphinic acid. 




rc2H5 


fC2H5 




P \ C2H5 


PO \ C2H5 




(C2H5 


iC2H5 




Triethylphosphine. 


Triethylphosphine oxide. 



538 ELEMENTS OF MODERN CHEMISTRY. 

The compounds of arsenic and ethyl are entirely analogous 
to the phosphines ; they have already been alluded to. Besides 
these, there are ethylic combinations corresponding to cacodyl 
and its derivatives. 

SILICON-ETHYL. 

Si(C2H5)4 

This compound is obtained by treating silicon chloride with 
zinc ethyl. 

SiCl* + 2Zn(C2H5)2 = 2ZnCP + Si(C^HS)* 

Silicon- tetrethyl is a colorless, mobile liquid, not decomposed 
by water, combustible, burning with a brilliant white flame and 
production of white fumes of silicic acid. It is indifferent to 
the action of reagents, and acts in all points like a hydrocarbon, 
C(C^H^)* = C^H^°, in which one atom of carbon is replaced by 
an atom of silicon. Its analogue, silicon-methyl, a liquid boil- 
ing at 30°, corresponds to tetramethylmethane, C'^H^^, a hydro- 
carbon boilin": at 10°. 



'o 



Si(C^H5)* Si(CH^)* C(CH^)* 

Silicon-ethyl. Silicon-methyl. Tetramethylmethane. 

The following facts, discovered by Friedel, show the analogy 
between these compounds of silicon and the corresponding hydro- 
carbons : 

When silicon-ethyl is submitted to the action of chlorine, an 
atom of hydrogen is exchanged for an atom of chlorine, and 
the chloride Si(C'H*Cl)(C'H5)^ is formed. The latter is a liquid 
boiling at 185°, and can have its chlorine atom replaced by 
other atoms or groups, like the alcoholic chlorides. When dis- 
tilled with potassium acetate, it yields the corresponding acetate, 
(C'H5)3Si-eH^O.C'H^O, which may be saponified by potas- 
sium hydroxide, like an alcoholic acetate, the oxyacetyl group, 
OC^H^O, being replaced by a hydroxyl group. The alcohol so 
formed, (CH^lSi-C^H^OH, has been named by Friedel silico- 
nonyl hydroxide, on account of its analogy with nonyl hj^droxide. 

SiC^H^^OH C^H^IOH 

Silicononyl hydroxide. Nonyl hydroxide. 

It is a colorless liquid, insoluble in water, and boiling at 
190°. 



ORGANO-METALLIC COMPOUNDS. 539 

OEQANO-METALLIC COMPOUNDS. 



ZINC-ETHYL. 

Zn^^(C2H5)2 

One of the more important of the compounds formed by the 
Unftn of the metals with alcoholic radicals is zinc-ethyl, dis- 
covered by Frankland. 

It is prepared by heating ethyl iodide with zinc-turnings 
and a small quantity of sodium on a water-bath. Zinc iodide 
and zinc-ethyl are formed. When the reaction is terminated, 
the product is distilled and that portion collected which passes 
above 115^. All these operations are conducted in an at- 
mosphere of carbon dioxide. 

Zinc-ethyl is a colorless, mobile, and highly-refractive liquid. 
It has a peculiar, penetrating, and very disagreeable odor. It 
boils at 118°. It takes fire spontaneously on contact with the 
air, burning with a green flame, and producing white fumes 
of zinc oxide. 

If water be added to a small quantity of zinc-ethyl contained 
in a tube, a brisk eflervescence at once takes place, and a white 
deposit is formed. The gas is ethane, and the deposit is zinc 
hydrate. 

Zn(C'H5)2 -f 2W0 = Zn(OH)^ + 2C'H« 

Zinc-ethyl will enter into double decompositions, and is 
much used in the synthesis of organic substances. 

By the action of phosphorus trichloride on this body, Hof- 
mann and Cahours obtained triethylphosphine and zinc chloride. 

There is a zinc-methyl^ Zn(CH^)^, corresponding to zinc- 
ethyl. 

MERCUE-METHYL AND MERCUR-ETHYL. 

These compounds were obtained by Frankland and Duppa, 
by the action of methyl and ethyl iodides on sodium amal- 
gam, in presence of a small quantity of acetic ether. 

Mercur-etJiyl is a colorless, inflammable liquid, insoluble in 
water. Density, 2.44. Boiling-point, 158-160°. It is one 
of the most dangerous poisons known. The inhalation of its 
vapor, even in small quantity, will produce fatal poisoning. 



540 ELEMENTS OF MODERN CHEMISTRY. 

Chlorine, bromine, and iodine instantly decompose mercur- 
ethyl with formation of a compound of mercur-monethyl. 

Hgjgl' + r = cm + HgjfH^ 

Mercui-ethyl. Ethyl iodide. Mercur-monethyl iodide. 

STANNETHYLS. 

The discovery of the numerous compounds of tin and efhjl 
is due to Lowig. Their history has been completed by Frank- 
land, Cahours, and Riche. 

As the nomenclature and constitution of the stannethyls 
have already been indicated (page 457), we need only consider 
a few of these interesting compounds. 

Stanno diethyl, Sn(C^H^)l — The iodide of this compound 
is obtained when ethyl iodide is heated with tin-filings to about 
180°. This iodide, Sn(CTI^)'r, purified by crystallization in 
alcohol, furnishes free stannodiethyl when its solution is treated 
with zinc, which removes the iodine. 

Stannodiethyl is an oily, yellow liquid, which does not vola- 
tilize without decomposition. When heated to 150° it begins 
to boil, but the greater part of it is decomposed into stanno- 
tetrethyl and tin. 

2[Sn(C^H^)2] = SniC'Wy + Sn 

The iodide of stannodiethyl crystallizes in pale yellow needles. 
In its solution, the alkalies precipitate the oxide Sn(C^H^)^0, 
which forms an amorphous, white precipitate, insoluble in water 
and alcohol, but soluble in the alkalies and acids with which it 
forms salts. 

Stannotriethyl or Sesquistaimethyl, SnXC'HS)^ = (C'H^)' 
Sn-Sn(C'^H^)l — This is formed, together with the preceding 
compound, by the reaction of ethyl iodide on an alloy of tin and 
sodium. It is separated by fractional distillation ; it boils between 
265 and 270°. It plays the part of a radical and combines 
directly with oxygen. The oxide contains Sn^(C^H^)^0 = 
[Sn(C^H^)^]^0. It combines with the elements of water, form- 
ing a hydrate, Sn(C^H^)lOH, crystallizable in prisms. These 
crystals are fusible at 44°. The oxide distils at 272°. It 
reacts with the acids to form crystallizable salts. 

[Sn(C^H0^]2O H- 2HN0^ = 2[Sn(C^H^)lN0T + H^O 

stannotriethyl oxide. Stannotriethyl nitrate. 



VOLATILE FATTY ACIDS. 541 

The iodide, Sn(C^H^)^I, is a liquid having a mustard-like 
odor, and distilling without decomposition towards 235-238°. 
Density at 15°, 1.833. 

Stannotetrethyl, Sn(C^H^)*. — Colorless liquid, almost odor- 
less, and boiling at 181°. Density, 1.187. It is formed by 
the action of zinc ethyl on stannodiethyl iodide. 
Sn(C^H5)^P + Zn(C^H^)2 = Sn(C^H^)* + ZnP 

Stannnodiethyl iodide. Zinc-ethyl. Stannotetrethyl. 

It is a saturated compound, and does not enter into combi- 
nation, but by the action of energetic reagents it yields com- 
pounds of stannodiethyl or stannotriethyl. Thus, with iodine, 
the following reaction takes place : 

SnCC^H^)^ + r = Sn(C'HO'I + C'Wl 



VOLATILE FATTY ACIDS DERIVED 
FROM. THE ALCOHOLS. 



Modes of Formation and Constitution. — These acids result 
from the oxidation of the alcohols of which the principal com- 
pounds have been described. They are formed in a great num- 
ber of reactions, and many of them exist already formed in 
nature, either in the free state or in combination in neutral 
fatty compounds, that is, the oils and fats. 

Their composition is expressed by the general formula C"H^" 
0^ ; they contain one more atom of oxygen and two atoms of 
hydrogen less than their corresponding alcohols. 

Their principal modes of formation are as follows : 

1. By oxidation of an alcohol : 

CH^O -i- 0' = CH^O^ -I- H^O 

Methyl alcohol. Formic acid. 

2. By oxidation of an aldehyde : 

Aldehyde. Acetic acid. 

3. By the decomposition of an organic cyanide with boiling 
potassium hydroxide : 

Methyl cyanide. Potassium acetate. 

46 



542 ELEMENTS OP MODERN CHEMISTRY. 

The acetic acid is formed in this last reaction, by the union 
of the carbon of the cyanogen group with the oxygen of both 
the potassium hydroxide and the water, the hydrogen of these 
two bodies combining with the nitrogen of the cyanogen to 
form ammonia. It may then be admitted that acetic acid con- 
tains a radical carbonyl, CO, united on the one hand with a 
methyl group (that of the methyl cyanide), and on the other 
with a hydroxyl group, OH. 

The other acids of the series possess an analogous constitu- 
tion. 

CH3 C2H5 C3H7 C4H9 

CO.OH CO.OH CO.OH CO.OH etc. 

Acetic acid. Propionic acid. Butyric acid. Valeric acid. 

4. A method of synthesis, discovered by Wanklyn, furnishes 
a direct support to this theory of the constitution of the fatty 
acids. That chemist realized the synthesis of acetic and pro- 
pionic acids by passing a current of carbonic acid gas over 
sodium-methyl and sodium-ethyl, organo-metallic compounds 
which result from the action of sodium upon zinc-methyl and 
zinc-ethyl. 

NaCHS + CO.O = ?^^ 

CO.ONa 
Sodium-methyl. Sodium acetate. 

C2H& 
]S[aC2H5 + CO.O = I 

CO.ONa 
Sodium-ethyl. Sodium propionate. 

General Properties. — 1. The volatile fatty acids of the series 
Qnjj2nQ2 ^j.g niouobasic ; each contains one atom of hydrogen 
which may be replaced by an equivalent quantity of a metal. 

2. When submitted to dry distillation, many of their salts 
yield a ketone and a carbonate. 

CH3-C0.0^(. ,, _ 
CH3-C0.0^^^ 

Calcium acetate, 

3. The same reaction may produce an aldehyde and a hydro- 
carbon of the series CH^" (Chancel). 

C3H7 

(C3H7-CO.O)2Ca = ,4- C3H6 -f- CaCOS 

CHO 
Calcium butyrate. Butaldehyde. Propylene. 



CH3 




CO 


+ CaC03 


CH3 
cetone 


Calcium carbonate. 



FORMIC ACID. 543 

4. When a mixture of a salt of a fatty acid and a formate 

is subjected to dry distillation, the principal product of the 

reaction is an aldehyde (Piria). 

CH3 
CH3-C0.0K + H-CO.OK = i + K'^GO^ 

CHO 
Potassium acetate. Potassium formate. Aldehyde. 

5. The fatty acids are converted into chlorides by the action 
of phosphorus pentachloride, or oxy chloride (G-erhardt). 

C2H30.0K + PC15 = C2H30.C1 + P0C13 + KCl 
Potassium acetate. Acetj'l chloride. Phosphorus 

oxychloride. 

6. By the action of these chlorides upon the salts of the 
fatty acids, the anhydrides of the acids are formed (G-erhardt). 

C^H^^JO + C2H3.0C1 = KCl + g™}0 
Potassium acetate. Acetyl chloride. Acetic anhydi-ide. 

7. When subjected to the action of phosphoric anhydride, 
the ammonium salts of these acids lose 2H^0 and are con- 
verted into nitriles or cyanogen ethers (Dumas, Malaguti and 
Le Blanc, Frankland and Kolbe). 

CH3 CH3 

I = 2H20 + I 

C0.0(NH4) ^ CN 

Ammonium acetate. Acetonitrile. 

(Methyl cyanide.) 

FORMIC ACID. 
CH202 

This acid, which was discovered by S. Fischer in 1760, in 
red ants, is formed in a great number of reactions, particularly 
in the oxidation of methyl alcohol, in the decomposition of 
hydrocyanic acid by acids or alkalies, in the distillation of oxalic 
acid, and in the oxidation of many organic matters, such as 
starch, sugar, etc. Berthelot achieved its direct synthesis by 
heating carbon monoxide for a long time to 100° in sealed 
flasks containing a concentrated solution of potassium hydrate. 

CO + KOH = HCO.OK 

Potassium formate. 

Preparation. — Formic acid is best prepared by heating 
oxalic acid with glycerol ; the latter is found unchanged after 
the reaction, but the oxalic acid is decomposed according to 
the equation C^O^H^ = H.COOH -f COl 



544 ELEMENTS OF MODERN CHEMISTRY. 

Equal weights of the two substances are heated to about 
110° in a retort connected with a condenser; carbon dioxide 
is disengaged and dilute formic acid distils over. When the 
action has ceased, a fresh quantity of oxalic acid is added and 
the heating continued ; the same decomposition takes place, 
but a more concentrated formic acid (56 per cent.) collects 
in the receiver. As the glycerol does not suffer a permanent 
change, the operation may be made continuous by adding 
fresh quantities of oxalic acid to the retort. 

Anhydrous formic acid is prepared by decomposing the dry 
lead salt in a current of hydrogen sulphide. 

(HCOO)Tb + H^S = 2HC00H + PbS 

Properties. — Formic acid is a colorless liquid, having a 
pungent odor and a very acid taste. It boils at 101°, and solid- 
ifies to a crystalline mass at 8.5°. It mixes with water in all 
proportions. 

If an excess of sulphuric acid be added to a small quantity 
of formic acid contained in a test-tube, and a gentle heat be 
applied, a regular disengagement of gas will take place ; it may 
be ignited at the mouth of the tube, and will burn with a blue 
flame. It is carbon monoxide, formed according to the equa- 
tion CH^O^ == CO -h H^O. 

If formic acid be added to solution of silver nitrate, and 
the liquid heated, it soon becomes clouded ; silver is pre- 
cipitated, and carbon dioxide disengaged. The formic acid 
becomes oxidized in reducing the silver nitrate. 
CH^O^ + = CO^ + H^O 

Chlorine determines an analogous decomposition. 
CH^O^ + CP = CO' + 2HC1 

Formates. — Formic acid is an energetic acid, perfectly neu- 
tralizing the bases. It is monobasic; one of its hydrogen 
atoms can be replaced by an equivalent quantity of metal. The 
formates are soluble ; the most characteristic are cnpric for- 
mate^ Cu(CHO')' -j- 4H^0, which crystalHzes in magnificent, 
obHque rhombic prisms, and lead formate, Pb(CHO'/, which 
forms long, colorless needles, slightly soluble in cold water. 

Ammonium formate, which is obtained by saturating formic 
acid with ammonia, crystallizes in prisms which are very solu- 
ble in water. When quickly heated to about 200°, it breaks 
up into hydrocyanic acid (formonitrilc) and water (Pelouze). 
(NH*)CHO' = 2H^0 + CNH 



ACETIC COMBINATIONS. 545 

FORMALDEHYDE. 

CH20 = H-CHO 

Hofmann obtained this body by the slow combustion of 
methyl alcohol, brought about by a spiral of platinum wire. 
CH^O + = H^O + CH^O 

It is also formed in the distillation of barium and calcium 
formates. Formaldehyde is known only as a vapor at high 
temperatures, and in aqueous solution. The latter has a 
pungent odor and powerful antiseptic properties ; " formalin" 
is a 40 per cent, solution of it used as an antiputrescent and 
caustic. On evaporation of its aqueous solution, formalde- 
hyde becomes polymerized, an amorphous solid called para- 
formaldehyde being produced. Dilute solutions of alkaline 
hydroxides convert the aldehyde into formose^ a mixture of 
polymers containing acrose, (CH^O)®, related to the sugars. 



ACETIC COMBINATIONS. 

It may be assumed that these compounds contain the mon- 
atomic radical acetyl (C'H^O)' = (CH'-CO)', which may be 
regarded as oxidized ethyl. 

(C2H5)' = I (C2H30)' = I 

^ -CH2 ^ -co 

Ethyl. Acetyl. 

Diacetyl contains twice this radical, aldehyde is the hy- 
dride, and acetic acid the hydroxide. Besides these, there 
are known the oxide and chloride of acetyl, methyl acetyl 
(acetone), acetyl ammonia or acetamide, etc. 

The following formulae indicate the relations of these bodies : 

C2H30.C^H30 C2H30.0H 

Diacetyl. Acetyl hydrate (acetic acid). 

C2II30.H (C2H30)20 

Acetyl hydride (aldehyde). Acetyl oxide (acetic anhydride). 

C2H30.CI C2H30 ) 

Acetyl chloride. H i- N 

C2H30.CH3 hJ 

Acetyl methylide (acetone). Acetamide. 

ACETIC ACID. 

C2H<02 
Acetic acid is the acid of vinegar. It is the product of the 
oxidation of alcohol. It is formed in a number of other reac- 
tions, among which we may mention the oxidation of aldehyde, 
kk 46* 



546 



ELEMENTS OF MODERN CHEMISTRY. 



the decomposition of metliyl cyanide by potassium hydrate, the 
action of carbon dioxide on sodium-methyl, and the dry distil- 
lation of a great number of organic substances, such as wood, 
starch, gum, sugar, etc. 

Preparation. — The large quantities of acetic acid employed 
in the arts are obtained by the destructive distillation of wood. 

The operation is conducted in large iron cylinders, heated 
directly by a fire (Fig. 123). The products of the distillation 




consist of liquids and gases. The liquids are condensed in a 
large worm, tt, cooled by a continual circulation of cold water 
through surrounding pipes mm ; the gases are conducted back 
to the fire-grate by the pipe h. The condensed product consists 
of an aqueous portion and of tar. The greater part of the 
latter is separated by a new distillation ; the first portions 
which pass contain wood-spirit, after which acetic acid distils. 
Tlie acid liquid is neutralized by lime, and the calcium ace- 
tate formed is converted into sodium acetate by adding a solu- 
tion of sodium sulphate. The liquid, separated by filtration 
from the calcium sulphate, yields on evaporation sodium ace- 
tate, still colored brown by tarry matters. The latter are 
destroyed by frying the salt, that is, by heating it for some 
time to 250°, a temperature which carbonizes the tar but does 
not a.ff"ect the sodium acetate. The mass is then exhausted 
with water, the solution filtered, concentrated, and crystallized. 
Crystals of pure sodium acetate are thus obtained, a salt which 
was formerly called ]pyrolignite of soda. Acetic acid is pre- 



ACETIC ACID. 



547 



pared by drjdng this salt and distilling it with -| its weight of 
concentrated sulphuric acid. 

Or the dry salt may be decomposed by an exact quantity of 
sulphuric acid. The acetic acid which separates from the 
sodium sulphate may then be decanted, and cooled in a freez- 
ing mixture. The portion remaining liquid is separated and 
the solid mass constitutes pure acetic acid. 

Vinegar. — Vinegar is the product of the acid fermentation 
of wine and other alcoholic liquids. The following process is 
largely employed for the conversion of wine into vinegar. It 
is the Orleans process. A small quantity of warm vinegar is 
first introduced into large vats, which have already been used 
for the operation and are impregnated with the peculiar fer- 
ment formed ; quantities of wine are then added at intervals 
of several days, the vats being maintained at a temperature 
between 24 and 27°. In a fortnight, the acetification is com- 
plete, and a portion of the vinegar is withdrawn and replaced 
by a new quantity of wine which also becomes converted into 
vinegar. The process is thus continuous. Under these cir- 
cumstances, the alcohol is converted into acetic acid by the 
influence of a peculiar ferment that is called mother of vinegar. 
It is a vegetable product, , | 

amycoderm(J[^co6?er??ia \ ™ 

aceti), which appears on 
the surface of the liquid, 
where it absorbs oxygen 
from the air and subse- 
quently cedes it to the 
alcohol (Pasteur). Its 
action may be compared 
to that of platinum black. 
By another process, a 
mixture of weak alcohol, 
water, and albuminoid 
matter (the juice of pota- 
toes, beets, etc.), contain- 
ing the elements neces- 
sary for the production of 
the ferment, is allowed to 
trickle over beech-wood 
shavings. The latter, which have been previously steeped in 
strong vinegar, are contained in a large cask, A (Fig. 124), 




Fig. 128. 



548 ELEMENTS OP MODERN CHEMISTRY. 

where tliey rest upon a double bottom perforated with holes. 
Tubes, tt^ pass through the upper portion, maintaining a current 
of air which enters at the lower portion of the cask. Under 
these conditions, the liquid, which spreads over the shavings 
and exposes a considerable surface to the air, becomes oxidized 
with such energy that the temperature soon rises to 30° ; a 
second passage of the liquid through the casks completes the 
acetification. 

Properties of Acetic Acid. — Acetic acid is solid below 1*7°, 
and crystallizes in large plates. It boils at 118°. Its density 
at 0° is 1.0801. Its odor is pungent and acid. It is very 
corrosive. It mixes with water and alcohol in all proportions, 
and when it is added to water there is a contraction in volume. 
The maximum contraction, and consequently the maximum 
density of aqueous acetic acid, corresponds to a mixture con- 
taining C^H^O^ -f H'^0. 

Vapor of acetic acid passed through an incandescent porce- 
lain tube yields gases and deposits carbon, at the same time 
forming small quantities of acetone, benzene, phenol, and 
naphthalene (Berth el ot). 

Phosphorus pentachloride converts acetic acid into acetyl 
chloride, with formation of hydrochloric acid and phosphorus 
oxy chloride. 

en^O.OH -f PCP = C^H^O.Cl + HCl + POCP 

Acetic acid. Acetyl chloride. 

If a mixture of small quantities of potassium acetate and 
arsenious oxide be heated in a test-tube, dense white vapors 
having an intense and disagreeable odor of garlic will be dis- 
engaged. 

This experiment permits the detection of minute traces of 
acetic acid ; if the latter exist in the free state in the liquid, 
its potassium compound must first be formed. The white 
vapor disengaged is due to a body formerly known as fuming 
liquor of Cadet (see page 496). 

ACETATES. 

The more important neutral acetates have the composition 
R'(C'H^O0 or K"(C'H^02)^ according as the metal which 
replaces the basic hydrogen of the acetic acid is univalent or 
bivalent. There are many basic acetates. 

Potassium Acetate, KC^H^O^ — This is prepared by satu- 



ACETATES. 549 

rating acetic acid witli potassium carbonate and evaporating to 
dryness. It is thus obtained in crystalline, very deliquescent 
laminae. It melts at 292°, and is very soluble in water. 

Sodium Acetate, NaC'H^O' + 3H^0.— This salt is obtained 
on a large scale in the arts in the manufacture of acetic acid. 
It was formerly called pyroUgiiite of soda. It crystallizes in 
large, oblique rhombic prisms, which are very soluble in water, 
and effloresce in dry air. 

Acetates of Lead.— Neutral lead acetate, PbCC^H^O')' + 
3H^0, known also as sugar of lead, is made by neutralizing 
acetic acid with litharge. It crystallizes in transparent, efflor- 
escent, oblique rhombic prisms, having a sweet and astringent 
taste. It dissolves in half its weight of cold water, and in 8 
parts of alcohol. It melts in its water of crystallization at 
75.5°. 

The neutral solution of lead acetate dissolves oxide of lead, 
forming different basic salts, according to the proportion of 
oxide dissolved. The more important of these are a dibasic 
acetate, Pb(C'H^O')' + PbO + 4H^0, and a tribasic acetate, 
PbCC'H^'O')' -I- 2PbO + nH^O. These two salts are gener- 
ally formed simultaneously when a solution of lead acetate is 
boiled with litharge. The solution thus obtained is used in 
medicine as Goulard's solution. If a few drops of it be added 
to ordinary river or well water, a cloud is produced, owing to 
the formation of lead sulphate and carbonate. 

If carbonic acid gas be passed into a solution of the sub- 
acetate of lead, a deposit of lead carbonate is formed. In this 
reaction, which serves for the preparation of white lead by the 
Clichy method, the excess of lead is removed from the subace- 
tate by the carbonic acid, neutral acetate being formed and 
remaining in solution. 

Acetates of Copper. — The neutral acetate Cu(C^H^O^)^ -j- 
H^O, is prepared by double decomposition by mixing hot solu- 
tions of sodium acetate and cupric sulphate. The cupric acetate 
is deposited on cooling in beautiful, oblique rhombic prisms 
of a deep bluish-green color. They dissolve in 5 times their 
weight of boiling water. The dilute aqueous solution is de- 
composed by boiling, a tribasic acetate being formed, while 
acetic acid is set free. 

When cupric acetate is heated, it first loses its water of crys- 
tallization, and decomposes when the temperature reaches 240 
or 250°, disengaging acetic acid, acetone, and carbon dioxide^ 



550 ELEMENTS OF MODERN CHEMISTRY. 

The residue is finely-divided copper. The product of the dis- 
tillation is a blue liquid, which, when rectified, yields colorless 
acetic acid mixed with a small quantity of acetone. It was 
formerly called radical vinegar. 

The name verdigris is applied to a basic acetate of copper 
consisting mostly of a dibasic acetate, Cu(C^H^O^)^ -f- CuO -|- 
6H^0. Verdigris is prepared by exposing to the air copper 
sheets piled up in layers with the pulp of grapes. In a few 
weeks the metal becomes covered with bluish crusts of verdi- 
gris, which are scraped off" and delivered to commerce in the 
form of light-blue balls. The alcohol, formed by the fermenta- 
tion of the sugar contained in the grape-pulp, becomes oxidized 
by the air and is converted into acetic acid, and under the in- 
fluence of the latter, the copper itself absorbs oxygen. Water 
and copper basic acetate are thus formed. 

Ferric Acetate, Fe(C^H^O^)l — The aqueous solution of 
this salt possesses a blood-red color. Boiling decomposes it, 
precipitating ferric hydroxide and liberating acetic acid. 
The salt is largely used as a mordant in dyeing. 

Silver Acetate, AgC^H^Ol — This salt, which is but slightly 
soluble in water, is precipitated when concentrated solutions 
of sodium acetate and silver nitrate are mixed. It is deposited 
from boiling water in brilliant, pearly, flexible plates, which 
darken on exposure to light. 

Ammonium Acetate, (NH*)C^IFOl — When acetic acid is 
saturated by a current of ammonia gas, this salt is obtained as 
a deliquescent, crystalline mass. It is very soluble in water 
and in alcohol. When heated, it first loses ammonia, then 
acetic acid, and acetamide finally distils. 

Nm.C^'ffO^ = WO + C^H^^O.NH^ 

Ammonium acetate. Acetamide. 

When distilled with phosphoric anhydride, ammonium 
acetate yields methyl cyanide, or acetonitrile. 

Ethyl Acetate, C^H^.C^ffO^, ordinarily known as acetic 
ether, is prepared by distilling a mixture of alcohol, sulphuric 
acid, and potassium or sodium acetate : ethyl acetate passes 
over, together with a certain quantity of alcohol which escapes 
the reaction. It is purified by agitation with a solution of 
calcium chloride, and the ether which floats is decanted, dried 
over calcium chloride, and rectified on the water bath. 



SUBSTITUTION PRODUCTS OP ACETIC ACID. 551 

It is a colorless liquid having a very agreeable, ethereal 
odor. It boils at 77°. Density at 0°, 0.9105. It is but 
slightly soluble in water, but dissolves in all proportions in 
alcohol and ether. Like all compound ethers, it is readily 
decomposed by potassium hydroxide. 

C^Hs.C^H^O^ + KOH = KC^H^O^ + C^H^.OH 
Ammonia converts it into acetamide and alcohol. 
C2H30.0C2H5 + NH3 = C^Hs.OH + C^HSQ.NHz 

It undergoes a remarkable reaction with sodium, which 
dissolves in it, forming sodium ethylate and the compound 
C^H^NaOl 

2[C2H30.0C2H5] + ITa^ = NaO-C^H^ + C^H^NaO' + H^ 

The body C^H^NaO' is the sodium compound of acetoacetic 
ether, Q'W'O' = CmXCm'0)0-OC'B.', which is derived 
from acetic ether, C^H^O-OC^H^, by the substitution of an 
acetyl group, C^H^O, for one atom of hydrogen in the radical 
acetyl. Free acetoacetic ether may be obtained by the action 
of dilute hydrochloric acid upon the sodium compound 
C^H^NaO^ It is a colorless liquid having an agreeable odor, 
and boiling at 182°. Density at 15°, 1.03. Sodium acetoacetic 
ether is extensively used in organic synthesis : it reacts readily 
with many halogen compounds, such as ethyl iodide, thus : 

CH'^-CO-CHNa-COO.C^Hs + C'Wl= 

Sodium acetoacetic ether. 

CH=*-CO-CH(C2H5)-COO.C^H5 + Nal 

Ethyl acetoacetic ether. 

The hydrogen of the CH group in the latter compound can 
be successively replaced by sodium and an alkyl group, thus : 
CH3-CO-CNa(C2H5)-COO. C^Hs and CH^-CO-C {Cm^y-COO. Cm^ 

Sodium ethyl acetoacetic ether. Diethyl acetoacetic ether, 

SUBSTITUTION PRODUCTS OF ACETIC ACID. 

Three chlorinated acids are derived from acetic acid : 

Monochloracetic acid C^HSCIG^ 

Dichloracetic acid C2H2C1202 

Trichloracetic acid C2HC1302 

Monochloracetic acid is formed when a current of chlorine 
is passed into acetic acid heated to 100°, and containing a 
small quantity of iodine. 



552 ELEMENTS OF MODERN CHEMISTRY. 

Monochloracetic acid is solid, and crystallizes in deliques- 
cent, rhomboidal tables or in prisms. It boils between 185 
and 187.8°. It is very corrosive. It is converted into glycollic 
acid when heated with an excess of potassium hydrate. 
KC^H^CIO' + KOH = KC'HXOH)0^ + KCl 

Potassium Potassium glycoUate. 

monochloracetate. 

Ammonia converts it into amidoacetic acid, C^HYNH^) 
O.OH. 

V^^^l + NH3 = HCl + ?^^-^^^ 
CO.OH CO.OH 

Monochloracetic acid. Glycocoll. 

Trichloracetic acid, C^HCPO^, a very important compound 
in the history of the science, was discovered by Dumas in 1840. 
It was then one of the most remarkable examples of a body 
formed by substitution, and a comparison of its properties with 
those of acetic acid led Dumas to announce the first idea of 
chemical types. 

It is obtained by exposing acetic acid to the action of a large 
excess of chlorine in direct sunlight ; more conveniently by 
oxidizing chloral with concentrated nitric acid (page 556). 

It forms transparent and deliquescent crystals, fusible at 
52.3°, and boiling between 195 and 200°. 

Its aqueous solution regenerates acetic acid by the action 
of sodium amalgam, an interesting reaction, since it furnished 
one of the first examples of inverse substitution (Melsens), as 
the replacement of chlorine by hydrogen is called. 

When boiled with potassium hydrate, trichloracetic acid fur- 
nishes potassium carbonate and chloroform. 
C^HCPO^ = CHCP + CO^ 



ACETIC ANHYDRIDE. 

(C2H30)20 

This important body, discovered by Grerhardt in 1852, is 
prepared by the action of one part of phosphorus oxychloride 
on three parts of dry sodium acetate. In this operation, acetyl 
chloride is first formed, and this reacts upon an excess of so- 
dium acetate, producing sodium chloride and acetyl acetate, or 
acetic anhydride. 

CWO.Cl + ^'^N°}0 = Na^' + c'ffo}*^ 

Acetyl chloride. Sodium acetate. Acetic anhydride. 



ALDEHYDE. 553 

Acetic anhydride is a colorless, mobile liquid, having a 
strong odor of acetic acid. It boils at 138°. When thrown 
into water, it sinks to the bottom, and, absorbing one molecule 
of water, is converted into acetic acid, which dissolves. It 
acts upon many other substances containing the hydroxyl 
group, forming acetyl derivatives. For example : 

2eH50H + (C'H^O)'O == H'O + 2C^H5.C='H^O^ 

ALDEHYDE, OR HYDRIDE OF ACETYL. 
C^H^O = CH3-CH0 

This body was discovered by Dobereiner in 1821 ; its com- 
position and principal properties were studied by Liebig. 

Preparation. — Aldehyde is prepared by oxidizing alcohol by 
heating it with manganese dioxide and dilute sulphuric acid, 
or better, with potassium dichromate and sulphuric acid. The 
vapors disengaged are condensed in a well-cooled receiver. The 
distilled liquid is rectified over calcium chloride, only the more 
volatile portion being collected. This is mixed with twice 
its volume of ether, and the ethereal solution saturated with 
ammonia gas. Crystals are deposited which constitute a com- 
bination of aldehyde with ammonia, and the aldehyde is ob- 
tained from them by adding a quantity of sulphuric acid exactly 
sufiicient to form ammonium sulphate with the ammonia; a 
gentle heat is applied, and the aldehyde vapor is passed through 
a tube filled with calcium chloride, and finally condensed in a 
well-cooled receiver (Liebig). 

Properties. — Aldehyde is a colorless, very mobile Hquid, hav- 
ing a penetrating and somewhat suffocating odor. It boils at 
21°. It mixes in all proportions with water, alcohol, and ether. 

It combines with ammonia, forming aldehyde-ammonia 
(Liebig). 

C^H^O.NH^ = C^H^O.NH* 

It unites with the alkaline acid- sulphites, forming crystal- 
lizable combinations. 

It is readily oxidized, being transformed into acetic acid. 

C^H^O -f O = C^H^O' 

If some aldehyde and a few drops of ammonia be added to 
a solution of silver nitrate, and a gentle heat be applied, the 
liquid soon becomes clouded, and the sides of the vessel con- 
taining it are covered with a brilliant deposit of metallic silver. 

T 47 



554 ELEMENTS OF MODERN CHEMISTRY. 

By tte action of sodium amalgam and water, aldehyde 
fixes two atoms of hydrogen, and is converted into alcohol 
(A. Wurtz). C^H^O + H^ =: C^H^O. 

When hydrochloric gas is passed into a mixture of aldehyde 
and absolute alcohol, monochlorether is formed. 

Cm^O + C2H5.0H + HCl = H20 + ^^^2H5>^ 

Monochlorether. 

Chlorine converts aldehyde into acetyl chloride and then 

into butyl chloral. 

C2H30.H + C12 = C2H30.C1 + HCl 
Acetyl chloride. 

Phosphorus pentachloride converts aldehyde into ethi/l- 
idene chloride, C^H*CP, thus : 

CH3 CH3 

I + PC15 = I + P0C13 

CHO CHC12 ^ 

Aldehyde. Ethylidene chloride. 

By the action of hydrochloric acid diluted with twice its 
volume of water, aldehyde doubles its molecule and is converted 
into a thick, colorless, neutral body, boiling at 95° in a vacuum ; 
it is soluble in water and reduces ammoniacal silver nitrate. 
This body is aldol, Q'WO'' (A. Wurtz). 

When heated with ordinary hydrochloric acid, aldehyde gives 
crotonic aldehyde (Kekule). 

Aldehyde. Crotonic aldehyde. 

The same transformation takes place when aldehyde is heated 
to 100° with a small quantity of zinc chloride and a trace of 
water. 

An important derivative of aldehyde, known as acetaldox- 
ime, results from the action of hydroxylamine upon aldehyde. 

CH3CH0 + H^NOH = CH3CHN0H + H20 

Hydroxylamine. Acetaldoxime. 

This body represents a numerous class, the oximes, which 
are formed by the reaction of hydroxylamine with bodies 
containing the carbonyl group. 

Phenylhydrazine, H^N-NH.C'ff (page 676), is another 
important reagent for compounds containing the carbonyl 
group. It forms with them condensation products known as 
phenyJliydrazones, water being eliminated. With aldehyde 
the reaction is expressed as follows : 

CH3.CH0 + H2N.NH.C6H5 = CH3.CH=N-NH.C6H5 + H20 



ACETYL CHLORIDE. 555 

Like all of its analogues, aldehyde can unite with hydro- 
cyanic acid, forming the compound CH^-CH(OH)(CN), a 
liquid soluble in water and alcohol, boiling at 183°, and con- 
verted by acids and alkalies into lactic acid, with disengage- 
ment of ammonia (see page 598). 

If sulphur dioxide be added to a dilute magenta solution 
until the latter is decolorized, the addition of a trace of alde- 
hyde will immediately restore the pink color. Nearly all the 
aldehydes respond to this test. 

When aldehyde is heated to 100° with alcohol, acetal is 
formed ; this is also found in small quantities among the 
products of the oxidation of alcohol. 

CHICHO + C^mOH ^ H^O -f- CH3CH<^^'[^5 

Aldehyde. Alcohol. Acetal. 

Polymerides of Aldehyde, — Aldehyde has a great ten- 
dency to become converted into polymeric modifications. 
Among these are paraldehyde^ which is liquid, and metalde- 
hyde, which is solid (Liebig). 

Paraldehyde, C^H^^O'^, is formed by the action of a trace of 
sulphuric acid or of zinc chloride on aldehyde. It is a color- 
less liquid, having a density of 0.998 at 15°, and boiling at 
124°. At a low temperature it solidifies to a leaf-like, crys- 
talline mass, fusible at 10.5°. It dissolves in eight times its 
volume of water. When distilled with a small quantity of 
sulphuric acid, it is again converted into aldehyde. 

ACETYL CHLORIDE. 

C2H30.C1=V 

COCl 

This body was obtained by Grerhardt in 1852, by treating 
sodium acetate with pentachloride, or oxychloride of phos- 
phorus. 
NaC^ffO^ H- PCP = C^H^OCl + NaCl + POCP 

Sodium acetate. Acetyl chloride. Phosphorus oxychloride. 

It is also formed by the action of chlorine on aldehyde. 

It is a colorless, mobile liquid, having a pungent odor. It 
boils at 55°. 

If it be poured into water, it sinks to the bottom, but rapidly 
decomposes into hydrochloric and acetic acids. 

CTFO.Cl f H^O = HCl + C^H^O.OH 



556 ELEMENTS OF MODERN CHEMISTRY. 

It undergoes a similar decomposition witli alcohol, forming 
ethyl acetate and hydrochloric acid. 

C^H^O.Cl + C^H^OH .:= HCl + C^HlC^ffO^ 
With ammonia, it forms acetamide and ammonium chloride. 

C'ff O.Cl + 2NH3 = NH*C1 + C'H^O.NH^ 
It reacts with acetates, forming acetic anhydride. 

CHLORAL, OR TRICHLORALDEHYDE. 

CCF 
C2C13HO = 7 

CHO 

This important body was discovered by Liebig and Dumas. 
It is formed by the prolonged action of chlorine on alcohol. 
It is a colorless, mobile liquid, having a peculiar, penetrating 
odor. It boils at 97.7°. 

Grerhardt regarded it as aldehyde in which the three atoms 
of hydrogen of the radical are replaced by three atoms of 
chlorine. 

C^H^O.H C^CPO.H 

Aldehyde. Chloral. 

(Acetyl hydride.) (Trichloracetyl hydride.) 

Its reactions resemble those of aldehyde. It forms crystal- 
lizable compounds with the disulphites. Its ammoniacal solu- 
tion reduces silver nitrate. These facts indicate that chloral 
contains the group CHO, characteristic of the aldehydes. 

It regenerates aldehyde by the action of nascent hydrogen 
(Personne). 

The caustic alkalies decompose it into chloroform and a 
formate (Dumas). 

C^HCPO 4- KOH = KCHO' + CHCP 

Chlox-al. Potassium formate. 

Nitric acid converts it into trichloracetic acid, in the same 
manner that aldehyde is converted into acetic acid. 

C'HCPO + == C^HCPO^ 

Chloral forms a crystallizable compound with water, C^HCPO 

CCP 
-1- H^O = I ' called chloral hydrate. The latter 

CH(0H)2 -^ 

melts at 57°, and boils at 98° (Personne), being at the same 

time decomposed into anhydrous chloral and water. It is very 

soluble in water. 



ACETONE. SST 

In contact with concentrated sulphuric acid, chloral is 
rapidly converted into a white, solid substance which is insol- 
uble in water ; it has the same composition as ordinary chloral, 
and is called insoluble chloral. 

Chloral also combines with alcohol, forming alcoTiolate of 
chloral (Personne). 

Chloral hydrate has for some time been successfully employed 
in medicine as a soporific and anodyne (Liebreich). 

DIACETYL. 

(CH3.CO)2 
Two acetyl radicals which cannot exist alone unite together 
forming the interesting compound diacetyl. This has been 
obtained in various ways by reactions too intricate to describe 
here. It is a yellow liquid having a characteristic odor. It 
boils at 87°, and mixes readily with water and alcohol. Like 
other ketones, it will combine with hydroxylamine, and since 
it contains two carbonyl groups it is capable of forming a 
monoxime and a dioxime. The latter is highly characteristic, 
being a white crystalline body, insoluble in water. Its melt- 
ing-point is 234°. Diacetyl also combines with phenylhydra- 
zine and hydrocyanic acid. 

ACETONE. 
C3H60 

Acetone is the methylide of acetyl, C^H^O.CH^, and since 
acetyl itself is carbonyl (carbon monoxide) methylide, CH^-CO, 
acetone can be regarded as carbonyl dimethylide, CH^-CO-CH^. 

CO" IS . C0"fCH3 

Carbonyl chloride. Carbonyl dimethylide (acetone). 

Indeed, the synthesis of acetone has been made both by treat- 
ing acetyl chloride with zinc methyl (Pebal and Freund), and 
by treating sodium methyl with carbonyl chloride. 

Zn(CH3)2 + 2(C^H30.C1) = 2(C^H3O.CH0 + ZnCP 

Zinc methyl. Acetyl chloride. Acetone. 

2(CHlNa) + CO I ^} = 2NaCl + CO | ^^3 

Sodium methyl. Carbonyl chloride. Acetone. 

Preparation. — Acetone is prepared by distilling dry calcium 
acetate in a clay retort. The vapors given oiF are condensed 

47* 



558 ELEMENTS OF MODERN CHEMISTRY. 

in a well-cooled receiver, and the liquid obtained is distilled on 
a water-bath with an excess of calcium chloride. 

CaCC^H^O^)^ = C'WO + CaCO^ 

Properties. — Acetone is a colorless liquid, having a slightly 
empyreumatic, ethereal odor. It boils at 56°. It dissolves in 
all proportions in water, alcohol, ether, and wood-spirit. 

Like aldehyde, it forms crystallizable combinations with the 
alkaline acid-sulphites. 

Acetone and its homologues are not susceptible of direct 
oxidation. If it be heated with a mixture of sulphuric acid 
and potassium dichromate, it breaks up into acetic acid and 
formic acid, a portion of the latter being oxidized to carbon 
dioxide. 

CHICO.CH^ + 0^ =:= CH^-CO.OH + HCO.OH 

Nascent hydrogen, produced by sodium amalgam and 
water, converts it into secondary propyl alcohol (page 521). 

Besides isopropyl alcohol, the action of nascent hydrogen 
on acetone gives rise to a product of condensation of IP with 
two molecules of acetone, which is named pinacone. 

Pinacone. 

It is a tertiary glycol (see page 578). It constitutes a 
colorless, crystallizable mass, fusible at 42°, and boiling at 
172°. 

When acetone is added in small portions to phosphorus 
pontachloride, a very energetic reaction takes place and two 
chlorides are formed. One of them, C^H'^CP (methylchlor- 
acetol), boils at 70°. The other, C^H^Cl (monochloropropy- 
lene), boils at 23° (Friedel). 

C3H60 -I- POP = C^H'^CP + POCP 
C^H«CP = C^H^Cl + HCl 

Like aldehyde, acetone will unite with hydrocyanic acid, 
forming a cyanide (or cyanhydrin), which is decomposed by 
both acids and alkalies, with disengagement of ammonia and 
formation of an acid; the group CN is then converted in 
carboxyl CO.OH. 

^|3>C0 + HON = CH3>C<^^ 

Acetone. Acetone cyanhydrin. 



ACIDS OF THE SERIES C°h'^°0^. 559 

Acetone unites with hydroxylamine, forming a highly 
characteristic, colorless crystalline compound, acetoxime, 
which melts at 59°. 

CH3>C0 + H2N0H = ^g3>CN0H + H20 

With phenylhydrazine it condenses to acetone phenylhy- 
drazone, (CH^)^=N-NH.C^H^ a reaction which is likewise 
characteristic of bodies containing the carbonyl group. 

ACETAMIDE. 

C2H30.NH2 

This amide may be obtained by heating ethyl acetate to 100° 
in sealed tubes with aqueous ammonia. Alcohol and acetamide 
are formed according to the equation 

When the resulting liquid is evaporated in a vacuum, the 
acetamide remains. It may be purified by distillation, collecting 
that which passes above 200°. 

Acetamide is also formed by the action of ammonia on acetyl 
chloride ; one of the readiest methods of preparing it consists 
in simply distilling ammonium acetate. 

It is a solid, crystallizable body, soluble in water in all pro- 
portions. Its odor resembles that of mice. Boiling potassium 
hydrate reacts with it, forming potassium acetate and ammonia. 
Phosphoric anhydride removes from it the elements of water, 
converting it into acetonitrile or methyl cyanide. 

ACIDS OF THE SERIES C"H^"0^ 

Formic and acetic acids, of which the principal derivatives 
have just been described, are the first terms of a very extensive 
homologous series. It is the series of volatile fatty acids, so 
named because it includes a great number of compounds which 
were at first obtained from the natural fatty bodies, and which 
are the fatty acids proper. Among the bodies congeneric with 
acetic acid, those of which the molecules are less complicated 
are liquid at ordinary temperatures ; the others are solid. The 
following table gives the nomenclature, composition, and prin- 
cipal physical properties of these acids : 



560 



ELEMENTS OF MODERN CHEMISTRY. 



NAMES OF ACIDS. 


CETJDE 


EATIONAI, 


MELTING- 


BOILING^ 




FORMULA. 


FOEMUL^. 


POINTS. 


POINTS. 


Formic acid . . 


. . CH202 


H-CO.OH 


8° 


101° 


Acetic acid . . . 


. . C2H402 


CH3-C0.0H 


17° 


118° 


Propionic acid 


. C3H602 


C2H5-CO.OH 


—36.5° 


140.7° 


Butyric acid . . 


. C*H802 


C3H7-CO.OH 


0° 


163° 


Valeric acid (isovaleric) C5Ili0O2 


C4H9-C0.0H 


—51° 


175° 


Caproic acid (isocaproic) C6H1202 


C5H11-C0.0H 


8° 


205° 


(Enanthylic acid . 


. . C7Hi*02 


C6Hi3_CO.OH 


—10.5° 


212° 


Caprylic acid . . 


. C8H1602 


C7H15-CO.OH 


16.5° 


236° 


Pelargonic acid 


. . C9H1802 


C8Hn-C0.0H 


12.6° 


260° 


Capric acid . . . 


. C10H20O2 


C9H19-CO.OH 


31.4° 




Laurie acid . . . 


. C12H2402 


C11H23-CO.OH 


43.6° 




Myristic acid . . 


. C1*H2802 


C13H27-CO.OH 


53.8° 




Palmitic acid . . 


. C16H3202 


C15H31-CO.OH 


62° 




Margaric acid . . 


. 01^3*02 


C16H33-CO.OH 


60° 




Stearic acid . . . 


. C18H3602 


C17H35-CO.OH 


69.2° 




Arachnic acid . . 


. C20H40O2 


C19H39-CO.OH 


75° 




Benic acid . . . 


. C22H4402 


C21H43-CO.OH 


96° 




Cerotic acid . . 


. C27H5402 


C26H53-CO.OH 


78° 




Melissic acid . . 


. C30H6002 


C29H59-CO.OH 


88° 





We have already noticed the existence of numerous isomeric 
alcohols, and in their study the principles of isomerism have 
been explained. Such isomerides exist also in the series of 
acids, and are caused by the different atomic structure of the 
radicals, C"H'^"+\ which figure in the preceding formulae. We 
will consider two examples. 1. When normal butyl alcohol, 
CH^-CH^-CH^-CHIOH, is oxidized, normal butyric acid, or 
the butyric acid of fermentation, is obtained, CH^-CH^-CH^- 
CO.OH. The acid obtained by oxidation of the butyl alcohol 
of fermentation is different from this, and the difference is 
caused by the difference in structure of the radicals (C^H^)'. 

Isobutyric acid, derived from the alcohol of fermentation, 

whose constitution is pTT3^CH-CH^0H, contains prrs^ 

CH-CO.OH. 

The acid is derived from the alcohol by the substitution of 
for H^ in the group (CHIOH)'. 

2. As we have already seen, the constitution of amyl alcohol 
of fermentation is expressed by the formula 

The valeric acid produced by its oxidation is then 
Qg3>CH-CH2-CO.OH 



PROPIONIC ACID. 561 

Normal valeric acid results from the oxidation of normal 
amyl alcohol, and contains 

CH3-Cff-CH^-CH=^-C0.0H 

QJJ3 

Methylethylacetic acid, pjrrs^CH-CO.OH, or optically 

active valeric acid, is derived from active amyl alcohol. 

The trimethylacetic acid, which was discovered by Butlerow, 
contains (CH^)^C-CO.OH ; it is derived from the alcohol 
(CH^yC-CHlOH, which is not known. 

If we compare the three isomeric acids, C^H^°0^ with acetic 
acid itself, we will find that their isomeric relations can be ex- 
pressed in a very simple manner, by saying that normal valeric 
acid is propylacetic acid, the acid derived from the alcohol of 
fermentation is isopropylacetic acid, and that the last two are 
methylethylacetic and trimethylacetic acids. 

CH3 CH2(C3H7) CH2(CH<^23) 

CO.OH CO.OH CO.OH 

Acetic acid. Propylacetic acid. Isopropylacetic acid. 

CH<^2H5 C(CH3)3 

CO.OH CO.OH 

Methylethylacetic acid. Trimethylacetic acid. 

The foregoing facts are sufficient to elucidate the isomerism 
of acids of the series C^B.'^'OK 



PEOPIONIC ACID. 

C3H602 = CH3-CH2-CO.OH 
This acid is formed by the action of potassium hydrate on 
ethyl cyanide. It is also a product of fermentation ; thus, it 
has been obtained by allowing a solution of sugar, mixed with 
chalk and cheese, to ferment during a year. It is also formed 
in small quantity in the distillation of wood. 

Wanklyn made its synthesis by passing carbon dioxide over 
sodium ethyl. 

CO.O + C'Wm = C^H^-CO.ONa 

Sodium propionate. 

It is most conveniently prepared by oxidizing normal 
propyl alcohol by means of chromic acid (Pierre and 
Puchot). 

CH^-Cff-CH^.OH + 0^ = CH^CH^COOH + H=^0 

II 



562 ELEMENTS OP MODERN CHEMISTRY, 

Properties. — It is a colorless, mobile liquid, having an odor 
like that of acetic acid. It solidifies at — 36.5°, and boils at 
140.7°. Density at 21°, 0.996. It is miscible with water in 
all proportions. Calcium chloTide separates it from its aqueous 
solution. 

There are a great number of substitution products directly 
related to propionic acid. Among these are the chlorine, bro- 
mine, and iodine derivatives, and the amides. Two of these 
derivatives are known of each particular species, presenting 
curious isomeric relations. The following examples will serve 
as illustrations : 

CH3 CH3 CH2C1 CH3 CH2(NH2) 

CH2 CHCl CH2 CH(NH2) CH2 

C02H C02H C02H C02H C02H 

Propionic a-Chloropro- jS-Chloropro- a-Amidopropi- /3-Amidopropi- 

acid. pionic acid. pionic acid. onic acid. onic acid. 

Only the iodo-derivatives will be described here, and farther 
on we will mention the amides. 

a-iodopropionic acid^ C^H^IO^, is prepared by the action of 
concentrated hydriodic acid or phosphorus iodide on lactic 
acid. 

CWO^ + HI = C^H^IO^ -f H^O 

Lactic acid. 

It is a thick, oily body, almost insoluble in water. 

13-todopropwmc acid is formed by the action of concentrated 
hydriodic acid or phosphorus iodide and water on glyceric 
acid. 

C^H«0* + SHI = C^H^IO^ -f 2H20 +r 

Glyceric acid. 

It is also formed by the direct combination of hydriodic acid 
and acrylic acid, C^H*0^. 

(;i3JJ4Q2 _|_ HI ^ C^H^IO^ 

It is a solid, occurring in crystalline laminae, fusible at 82°. 
It is very soluble in boiling water. When heated to 180° 
with hydriodic acid, it is converted into propionic acid. 
C^H^IO' + HI r= r + C^H^O' 

BUTYRIC ACIDS. 

C4H802 
Normal Butyric Acid, CH^-CH^-CH^-CO.OH, was dis- 
covered by Chevreul in butter, where it exists in combination 



BUTYRIC ACIDS. 563 

with glycerol in butyrin. Pelouze and G-elis have shown that it 
is formed in abundance when a solution of sugar, glucose, or 
even starch is abandoned for several weeks with the addition 
of chalk and old cheese. In about ten days a mass of calcium 
lactate is formed, but this soon disappears, gases being at the 
same time disengaged. The mass again becomes liquid, and 
the solution contains calcium butyrate. This is converted into 
sodium butyrate, which is finally decomposed by sulphuric 
acid ; the butyric acid separates in the form of an oily liquid, 
which is decanted and distilled. 

Properties. — Butyric acid is a colorless liquid, having a pun- 
gent and disagreeable odor which recalls that of rancid butter. 
It is quite soluble in water. Density at 14°, 0.958. Boiling- 
point, 163°. 

It perfectly neutralizes the bases, forming butyrates. These 
salts, which are mostly soluble in water, have a fatty aspect. 
Calcium butyrate, Ca(C*H^O^),^ is more soluble in cold water 
than in hot water, so that its cold saturated solution becomes 
a solid mass when heated to 70°. 

Butyrone, or Dipropyl Ketone. — When calcium butyrate 
is subjected to dry distillation, it yields, as principal product, 
butyrone, one of the homologues of acetone (Chancel). 
Ca(C*H^O'0' = (C3H^)^C0 -f CaCO^ 

Calcium butyrate. Butyrone. 

Butyrone is a colorless liquid, lighter than water, and having 
a peculiar, ethereal odor. It boils at 144°. 

Butaldehyde, C*H^O, is the principal product of the dis- 
tillation of a mixture of butyrate and formate of calcium. 
Ca(C*H^O0^ H- Ca(CHO^)^ = 2CaC0^ + 2C*H«0 

This important reaction, discovered by Piria, permits of the 
conversion of butyric acid into its aldehyde ; it can also l)e ap- 
plied to the transformation of other acids into aldehydes. 

Butaldehyde, which was discovered by Chancel, is a liquid, 
boiling at 74°. Like aldehyde, it forms a crystallizable com- 
pound with ammonia, unites with the alkaline acid-sulphites, 
and reacts with hydroxylamine and phenylhydrazine, as do 
the other aldehydes and the ketones. 

Isohutyric Acid, ^g3>CH-C0.0H, isomeric with bu- 
tyric acid, was discovered by Markownikow. 

It is formed by the oxidation of butyl alcohol of fermenta- 



564 ELEMENTS OF MODERN CHEMISTRY. 

tion, and exists naturally in the fruit of the Ceratonia siliqua 
(carob locust, St. John's bread). It is also obtained by decom- 
posing isopropyl cyanide with potassium hydroxide. 

(C^H^yCN + 2W0 = NH^ + (C^HO'-CO^H 
It is a liquid having a disagreeable odor, like that of the acid 

of fermentation. Density at 20°, 0.9503. It boils at 154°. 
Its calcium salt differs from that of the normal acid in 

being more soluble in hot than in cold water. 

YALEKIC ACIDS. 

C5H10O2 

Isovaleric Acid,QTT3>CH-CH2-CO.OH, was discovered 

by Chevreul, who obtained it from dolphin oil. It may be 
prepared by distillation of valerian root with water ; hence its 
name. It occurs also in angelica root and in Viburnum opulus. 
The same acid is formed when amyl alcohol is oxidized by a 
mixture of potassium dichromate and sulphuric acid. It is 
also formed when potassium hydrate is boiled with isobutyl 
cyanide, a reaction similar to that which has been indicated 
for the formation of isobutyric acid. 

^^3>CH-CH2-CN + 2H20 ^ NH^ + ^]|^3>CH-CH2-C0.0H 

Isobutyl cyanide. Isovaleric acid. 

Valeric acid is a colorless liquid, having a pungent, disagree- 
able odor. Density at 0°, 0.947. It boils at 175°. It dissolves 
in 30 parts of water, from which it is precipitated by the addi- 
tion of neutral salts. Its ammonium salt is used in medicine. 

Normal Valeric Acid, which has already been mentioned 
(page 561), is a colorless liquid, smelling like butyric acid. It 
boils at 184-185°, and its density at 0° is 0.9577. 

Methylethylaeetic Acid, ^2H5>CH-C0.0H, or optically 

active valeric acid, has been obtained by the oxidation of active 
amyl alcohol. It boils at 173°. 

Trimethylacetic Acid is formed when potassium hydrate is 
boiled with the cyanide derived from trimethylcarbinol. 

(CH3)^C-CN + 2H20 = (CH^)'C-CO.OH + NH^ 

It is a crystalline mass, fusible at 35°, and boiling at 163.8°. 
It dissolves in 40 parts of water at 20°. 



HIGHER FATTY ACIDS. 565 

CAPEOIC ACIDS. 

C6H1202 

There are at present known seven isomeric acids having the 
composition C^H^^O^ One of them was discovered in butter 
by Chevreul. Normal caproic acid is formed by the oxidation 
of normal hexyl alcohol, and in the decomposition of normal 
amyl cyanide by boiling potassium hydrate. It is an oily liquid, 
having but a faint odor ; its density at 0° is 0.945, and it boils 
at 205°. Leucine^ C^H^^NO^ an important nitrogenized body 
which exists in the animal economy, is an amide, C^II"(NII^)0^, 
of normal caproic acid. 

The caproic acid mentioned on page 560 is an isomeride of 
the preceding acid. It is obtained by decomposing, by potas- 
sium hydrate, amyl cyanide derived from the alcohol of fer- 
mentation. 

HIGHEH FATTY ACIDS. 

Our limited space will not permit of a description of all of 
the acids of this series ; we can only briefly consider the last 
members. 

Palmitic Acid, C^*^H^^Ol — This exists in palm-oil in com- 
bination with glycerol. It is prepared on a large scale by 
distilling palm-oil by means of superheated steam, which de- 
composes the oil into fatty acid and glycerol. The fatty acids 
solidify on cooling. The mass is expressed to remove the 
liquid oleic acid with which it is impregnated, and so obtained 
in dry, white cakes, which are used for the manufacture of 
candles. The pure acid melts at 62°. 

Margaric Acid, C^^H^*0^ — This acid was supposed by 
Chevreul to exist in most solid fats, but Heintz has shown 
that the so-called margaric acid derived from fats consists of 
a mixture of palmitic and stearic acids. Normal margaric 
acid was prepared synthetically by Kraff"t by decomposing 
cetyl cyanide by potassium hydroxide. 

C^«H3^CN -f 2H^0 = C^^H^^COOH -f NH^ 

It is said to exist in adipocere^ a waxy substance formed 
by the prolonged action of air and moisture on certain animal 
substances. 

Margaric acid crystallizes in white scales fusible at 60°, 
and soluble in alcohol and ether. 

48 



666 ELEMENTS OF MODERN CHEMISTRY. 

Stearic Acid, C^^H^^O^ was obtained from tallow by Chev- 
reul. It is a solid, melting at 69.2°. After cooling, tlie fused 
acid becomes a laminated, white mass. It is insoluble in 
water, but dissolves in alcoliol and ether. The alcoholic solu- 
tion deposits it in small pearly scales, which are not greasy to 
the touch. Stearic acid is used for the manufacture of stearin 
candles. 

The alkaline stearates are soluble in water. If a large excess 
of water be added to the solution of a neutral stearate, a crystal- 
line precipitate is formed which, according to Chevreul, is an 
acid stearate. On this reaction he has founded a method for 
the preparation of stearic acid. 

The stearates of calcium, barium, and lead are insoluble in 
water, and can be obtained by double decomposition. 

Cerotic and Melissic Acids. — These acids have been ob- 
tained from wax by Brodie (page 528). 



OLEIC ACID AND ITS HOMOLOaUES. 

Oleic acid, which has just been mentioned and which Chev- 
reul obtained from olein, is the principal constituent of a great 
number of oils and fats ; it does not belong to the series of 
volatile fatty acids. Its formula, C^^H'^^O^, shows that it differs 
from stearic acid by containing two atoms of hydrogen less 
than the latter acid. It belongs to the series CH^'^'^Ol 

AcryHc Acid, CH^^CH-CO.OH.— This is the first term 
of the series CIP^'^O^ It receives its name from the fact 
that it results from the oxidation of acrolein^ or acraldeliyde, 
C^H*0, which is formed in the destructive distillation of 
neutral fatty substances and glycerol and its compounds ; it 
is a product of the dehydration of glycerol. 

C3JJ8Q3 ^ Q3H4Q _|_ ^WO 

Glycerol. Acrolein. 

Acrolein reduces silver oxide, like the other aldehydes, 
being converted into acrylic acid. This acid is liquid, and 
boils at 140°. Like other unsaturated acids, it combines 
directly with nascent hydrogen, bromine, and the halogen 
acids. Fusion with potassium hydrate decomposes it into 
formic and acetic acids. A similar decomposition occurs 
with the other unsaturated acids. By fusion with alkaline 
hydroxides all are decomposed, yielding salts of two acids, 
but the split does not always take place at the double bond. 



OLEIC ACID. 567 

Crotonic Aldehyde and Acid. — These two bodies are 
homologues of acrylic aldehyde and acid. 

Cm^O acraldehyde. Cm'^0^ acrylic acid. 

C*H60 crotonaldehyde C^H^O^ crotonic acid. 

Crotonaldehyde is one of the numerous transformation 
products of ordinary aldehyde. When the latter body is sub- 
jected to the action of certain salts, it loses the elements of 
water and is converted into crotonaldehyde. 

This aldehyde is a liquid having a very irritating odor and 
an acrid taste. It boils at 103°. 

When submitted to the action of oxidizing agents, such as 
silver oxide in presence of water, it is converted into crotonic 
acid. 

This acid crystallizes in large plates, fusible at 72°. It boils 
at 182°. Nascent hydrogen, produced by the action of sul- 
phuric acid and zinc, converts it into normal butyric acid, 
CH^-CH^-CH^-CO.OH. It combines directly with bromine, 
producing heat, and is changed into dibromobutyric acid, 
CH^-CHBr-CHBr-CO.OH. Fusion with potassium hydrate 
decomposes it into two molecules of acetic acid. 

There is an isocrotonic acid^ CH^=:CH-CH^-CO.OH, a 
liquid boiling at 172°. When heated to 170-180° in sealed 
tubes, it is converted into crotonic acid. 

Oleic Acid, C^^H^^O^ — This acid, of which the preparation 
has been indicated (page 565), is an oily hquid, which solidifies 
to a crystalline mass at 4°. Its concentrated alcoholic solution 
deposits it, when cooled, in small needles fusible at 14°. 
Under a pressure of 10 m.m. it distils without decomposi- 
tion at 223°. When pure it is odorless, and does not redden 
litmus paper. On exposure to the air it absorbs oxygen, and 
becomes rancid and acid. Fusion with potassium hydrate 
converts it into acetic and palmitic acids. 

When boiled with nitric acid, it is oxidized, losing carbon 
dioxide, and there are formed volatile fatty acids from acetic 
to capric acid, and homologues of oxalic acid, including suberic 
(C^H^*0*) and succinic (C*H^O*) acids ; nitrogen peroxide con- 
verts oleic acid into an isomeride, elaidic acid, a solid body, 
crystallizing in brilliant plates, fusible at 44-45° (Boudet). 



C^Hio 


C6H14 


Butane. 


Hexane. 


C*H6(0H)* 


C6H8(OH) 


Erythritol. 


Mannitol. 



568 ELEMENTS OF MODERN CHEMISTRY. 



POLYATOMIC COMPOUNDS. 

After the description of the comparatively simple compounds 
which are naturally grouped with the monohydric alcohols, we 
proceed to the more complex compounds constituting the poly- 
hydric alcohols and their derivatives. The latter alcohols are 
neutral hydroxides, capable of reacting with the acids to form 
neutral combinations analogous to the compound ethers. Those 
better known are related to the saturated hydrocarbons, from 
which they are derived by the substitution of several hydroxyl 
groups for as many atoms of hydrogen. 

C2H6 C3H8 

Ethane. Propane. 

C2H*(OH)2 C3H5(OH)3 

Dihydroxyethane Trihydroxypropane 

(glycol). (glycerol). 

By oxidation of these polyhydric alcohols, acids are pro- 
duced which bear the same relation to the former that acetic 
acid bears to ordinary alcohol. 

It will be noticed that the radicals of these alcohols are un- 
saturated hydrocarbons, that is, they contain less hydrogen than 
the saturated hydrocarbons, C''H^"+^. Of these radicals, only 
those can exist in a free state which contain an even number 
of atoms of hydrogen. We will briefly consider the more 
important of them. 

ETHYLENE. 

C2H4 = CH2=CH2 

This gas, formerly known as olefiant gas or heavy carbu- 
retted hydrogen, is formed in a great number of reactions. It 
is produced, together with other hydrocarbons, when substances 
rich in carbon and hydrogen, such as fats and resins, are de- 
composed by dry distillation, that is, by the destructive action 
of heat. 

Preparation. — A mixture of 25 grammes of alcohol with 
150 grammes of sulphuric acid is heated in a 2-litre flask 
provided with a delivery-tube and a funnel-tube. When the 
evolution of gas begins, a mixture of 1 part alcohol and 2 
parts sulphuric acid is allowed to drop in slowly through tlie 
funnel-tube, and the gas is washed first through sulphuric 
acid and afterwards through potassium hydroxide solution. 
It may be collected over water. 



ETHYLENE. 569 

Towards the close of the operation the liquid blackens, and 
much sulphurous and carbonic acid gases are disengaged. 
These are absorbed by the caustic potash in the wash-bottle. 

The following equation expresses the reaction by which 
ethylene is formed : 

Composition and Properties. — Ethylene is a colorless gas, 
having a feeble, ethereal odor. Its density is 0.9784 compared 
to air, or 14 compared to hydrogen. It is liquefied by a press- 
ure of 60 atmospheres at 13° (its critical temperature), and the 
evaporation of the liquid under reduced pressures affords a 
valuable means of attaining low temperatures. Its composition 
may be deduced from the following experiment : 

2 volumes of ethylene (2 cubic centimetres, for example) 
and 6 volumes of oxygen are introduced into an eudiometer 
over mercury. After the passage of the spark, the 8 volumes 
will be found to be reduced to 4 volumes, all of which will be 
entirely absorbed if a solution of potassium hydrate be passed 
into the tube. The 4 volumes are therefore carbon dioxide. 

4 volumes of carbon dioxide represent 200^. 

2 volumes of ethylene therefore contain C^. 

4 volumes of carbon dioxide contain but 4 of the 6 volumes of oxygen 
employed ; the other two have therefore been used in the formation of 
water and have burned 4 volumes of hydrogen. 

2 volumes of ethylene then contain 4 volumes of hydrogen. 

Eudiometric analysis therefore indicates the composition 
of ethylene to be C'''H* = 2 volumes. 

This gas is inflammable and burns in the air with a brill- 
iant flame. When mixed with three volumes of oxygen and 
ignited, it produces a violent explosion. 

It is slowly absorbed by concentrated sulphuric acid, ethyl- 
sulphuric acid being formed. When ethylene is heated with 
hydriodic acid, the two bodies combine directly to form ethyl 
iodide. 

If one volume of ethylene and two volumes of chlorine be- 
rapidly mixed in a tall jar, and a lighted match be applied, the 
mixture takes fire and burns with a red flame extending to the 
bottom of the jar, which becomes covered with a black deposit 
of carbon. 

C'H* + 2CP =: 4HC1 + C' 

If equal volumes of ethylene and chlorine be mixed and ex- 
posed to diffused light on the pneumatic trough, the water will 

4:8* 



570 ELEMENTS OF MODERN CHEMISTRY. 

soon rise in the jar, and the two gases will disappear. At the 
same time, oily drops will appear on the sides of the jar and 
upon the surface of the liquid. The body so formed is a liquid 
insoluble in water, and results from the direct combination of 
ethylene and chlorine. It was formerly called Dutch liquid, 
or Dutch oil (hence the old name defiant gas) ; it is now called 
ethylene chloride. Its composition is expressed by the formula 
C'H^CP. It boils at 82.5°. 

If a small quantity of bromine be poured into a large flask 
filled with ethylene, and manipulated so that the bromine may 
form a thin layer on the sides of the flask, an elevation of tem- 
perature will be observed, and the liquid will rapidly become 
colorless. The bromine has combined with the ethylene to 
form a colorless liquid, ethylene bromide^ boiling at 131°. 

Ethylene iodide^ C^H*P, may be obtained by introducing 
iodine into large jars filled with ethylene, and exposing to dif- 
fused light during several days. The iodine gradually dis- 
appears and a white solid is formed which may be purified by 
crystallization in alcohol ; it is ethylene iodide. 

Chloro-Derivatives of Ethylene and Ethylene Chloride. — 
If ethylene chloride be heated with an alcoholic solution 
of caustic potash, a brisk reaction soon takes place. A gas 
is disengaged and may be collected over water ; on contact 
with a lighted taper, it burns with a flame tinged with green. 
This gas is chlor ethylene. It is formed according to the fol- 
lowing equation : 

C^H^CP + KOH = H^O + KCl + C'H^Cl 

Like ethylene itself, chlorethylene will combine directly with 
two atoms of chlorine, forming chlorethylene chloride, C^H^Cl. 
CP, which may also be obtained by the action of chlorine on 
ethylene chloride. 

Chlorethylene chloride is decomposed by alcoholic potash, 
like ethylene chloride. Water, potassium chloride, and dichlor- 
ethylene are formed. 

Q2H3QP _|_ g;QH ^ JJ2Q _|_ J^Ql _|_ C^H^CP 
Chlorethylene chloride. Dichlorethylene. 

In its turn, dichlorethylene can fix two atoms of chlorine, 
forming dichlorethylene chloride. 

These reactions have permitted the preparation of two 
classes of chloro-compounds, — one derived from ethylene chlo- 
ride, the other from ethylene itself. 



DENSITIES. 


BOILING-POINTS. 


1.256 at 12° 


82.5° 


1.422 at 17° 


115° 


1.576 at 19° 


137° 




158° 




182° 




—18 to —15° 


1.250 at 14° 


55° 




87 to 88° 


2.619 at 20° 


121° 



HOMOLOGOUS SERIES, C^H^'^. 571 



C2H4C13 ethylene chloride. 
C^H^CF chlorethylene chloride. 
C2H^C14 dichlorethylene chloride. 
C2HC15 trichlorethylene chloride. 
C^Cl^ carbon sesquichloride. 

C^H-i ethylene. 
C2H3C1 chlorethylene. 
C2H2C12 dichlorethylene. 
C2HC13 trichlorethylene. 
C2C1* tetrachlorethylene. 

Regnault, who carefully studied these bodies, has shown 
that the terms of the first series are isomeric with the chloro- 
derivatives of ethyl chloride, with the exception of the last 
two, which are the same in both series. 

That we may more thoroughly understand this isomerism, 
we will consider ethylene chloride, C'^H^Cl'^, and its isomeride 
dichlorethane, called also ethylidene chloride. In the first, 
two atoms of chlorine are united, each to a different atom of 
carbon ; in the second, both are united to the same carbon 
atom. 

CH2C1 CHC12 

CH2C1 CH3 

Ethylene chloride. Ethylidene chloride. 

TetracMor ethylene was discovered by Faraday in 1821. It 
is formed by the action of alcoholic potassium hydrate on tri- 
chlorethylene chloride. 

C^HCP = C^CP + HCl 

It is also formed by the action of a red heat on carbon 
sesquichloride. 

It is a very mobile liquid, which does not solidify at — 18°. 
It absorbs chlorine under the influence of direct sunlight, being 
transformed into carbon sesquichloride, C^CP. 

HOMOLOGOUS SERIES, C^H^"^ 

Ethylene is the first member of a long series of homologues, 
of which we will summarily describe a few of the others. Since 
ethylene is (CH^)^, the constitution of the higher members 
of the series, properly speaking, should be represented by the 
formula {QWy. 



572 ELEMENTS OF MODERN CHEMISTRY. 

Such bodies have been prepared, but they cannot be re- 
garded as the true homologues of ethylene. Their molecules 
do not contain any doubly-linked carbon atoms, and conse- 
quently they do not readily combine with the halogens. The 
superior homologue of ethylene is propylene, CH^-CH=CH^, 
and isomeric with this is trimethylene, which is represented 
by the formula 

CH2 
/ \ 
CH2-CH2 

Above the fourth member of this series, butylene, the 
number of isomerides increases rapidly. Thus, the butylene 
derived by dehydration from butyl alcohol of fermentation is 

gg3>C=CH2 

It is formed according to the following reaction : 
^^3>CH-CH2.0H — H20 ^ ^g3>C=CH2 

Independently of this butylene, there are two others, the 
formation and principal properties of which will be indicated 
farther on. 

Their constitutions are expressed by the formulae 

CH3-CH=CH-CH3 
CH3-CH2-CH^CH2 

The isomeric relations of these three butylenes may be repre- 
sented in a very simple manner if we consider them to be 
derived from ethylene, H^C=CH^, the hydrogen of which is 
partly replaced by methyl or ethyl. The following compounds 
are thus obtained : 

Dimethylettiylene a (CH3)2C=CH2, boils at —6°. 

Dimethylethylene ^ (normal) (CH3)HC=CH(CH3), boils at +3°. 
Ethylethylene (C2H5)HC=CH2, boils at —5°. 

The fifth member of the series, amylene or pentene^ C^H^'', 
presents still more numerous isomerides, but they can all be 
explained by the principles already exposed : they may be re- 
garded as derivatives of ethylene by the substitution of a pro- 
pylic or isopropylic group for one atom of hydrogen, or by the 
substitution of an ethyl group and a methyl group for two 
atoms of hydrogen, or lastly, by the substitution of three methyl 
groups for three atoms of hydrogen. 



PROPYLENES — BUTYLENES. 573 



PROPYLENES. 

C3H6 

Ordinary Propylene, CH^-CH=CH^ — To prepare this gas 
in a pure state Berthelot and de Luca heat allyl iodide with 
mercury and concentrated hydrochloric acid. 

2C=^H^I + 4Hg + 2HC1 = Hg^CF + Hg^P + 2C'H« 

It may also be made by allowing propyl alcohol to fall drop 
by drop on highly heated zinc chloride (Le Bel). 

Propylene is a colorless gas, having a feeble, alliaceous odor. 
It is rapidly absorbed by sulphuric acid, with formation of 
isopropylsulphuric acid (Berthelot). 

C3H6 + H2S0* =- (^^^^^^'>S0* 

It unites directly with hydriodic acid, forming an iodide 
which is isomeric with propyl iodide. C^H^ -\- HI = (C^H'^)'I 

Propylene unites directly with chlorine and bromine, forming 
propylene chloride, C^H*^CP, and propylene bromide, C^II^Br^ 
The latter is a colorless liquid, boiling at 145°. 

Trimethylene, / \ . — This remarkable body was first 
CW-CW 
described by Freund, who prepared it by heating with sodium 
the bromide, CH^Br-CH^-CH^Br. It is a gas which is 
absorbed by bromine more slowly than ordinary propylene, the 
normal bromide, boiling at 164-165°, being regenerated. It 
combines with hydriodic acid forming the iodide of normal 
propyl, CH^-CH^-CH^I. Normal propylene bromide is 
obtained by heating allyl bromide, C^H^Br, with hydrobromic 
acid. 

CH^^CH-CH^Br + HBr = CH^Br-CH^-CffBr 

Allyl bromide. Normal propylene bromide. 

It is a colorless liquid, boiling at 165°. 

BUTYLENES, C'W. 

1. Dimethylethylene «, (CH3)^C=CHl — This body is 
formed when isobutyl alcohol is dehydrated by zinc chloride, 
or by the action of alcoholic potassium hydrate on butyl iodide, 
C*H^I. It boils at — 6 ° . It unites directly with hydriodic acid, 
forming tertiary butyl iodide, (CH^)^CI-CII^, and combines 



574 ELEMENTS OF MODERN CHEMISTRY. 

witt bromine, forming the bromide (CH^)^CBr-CH'^Br, wMcli 
boils at 149°. 

2. Dimethylethylene /5 (normal or symmetric), (CH^)HC= 
CH(CH^). — Is formed by the action of alcoholic potash on 
secondary butyl iodide, CH^-CH^-CHI-CHl Boils at -f 3° 
and solidifies to a crystalline mass at 0°. Unites with HI, 
regenerating secondary bntyl iodide, and with bromine, forming 
the bromide (CH3)HBrC-CHBr(CH=^), which boils at 159°. 

Le Bel and Greene have obtained normal dimethylethylene 
by dropping ordinary isobutyl alcohol on highly heated zinc 
chloride ; the disengaged gases are passed through bromine, 
and the bromides of ^ dimethylethylene and ethylethylene — 
both gases are produced in the decomposition — separated by 
fractional distillation. 

De Luynes obtained secondary butyl iodide by reducing 
erythritol with a large excess of hydriodic acid (page 634). 

3. Ethylethylene (ethyl-vinyl), (C^HS)HC=CH^— Is ob- 
tained by the action of sodium on a mixture of ethyl iodide 
and bromethylene. 

C2H5I + BrHC=CH2 + Na2 = Nal + NaBr + (C2H5)HC=CH2 
Boiling-point, — 5°. It unites with HI, forming secondary 

butyl iodide, and with bromine, forming the bromide CH^- 

CH^-CHBr-CH^Br, boiling at 166°. 

AMYLENES, OB PENTENES, C^H^^. 

Several isomeric hydrocarbons are known of the composition 
Q5jjio_ They exist in unequal proportions in the product of 
the reaction of zinc chloride on amyl alcohol, a product gener- 
ally designated as amylene. It is prepared by heating amyl 
alcohol with zinc chloride, and passing the vapors given off into 
a well-cooled receiver. The product is rectified, that portion 
being retained which passes below 40°. It is a mixture of 
isomeric amylenes, whose boiling-points vary from 22 to 40°, 
and which result from the dehydration of amyl alcohol. 

Trimethylethylene or ordinary Amylene may be obtained 
in a pure state by dehydrating tertiary amyl alcohol (the 
hydrate of amylene of Wurtz), which may be accomplished 
by simply heating it. 

(CH3)2:=C(OH)-CH2-CII3 — H20 = (CH3)2C=CH(CH3) 
Tertiary amyl alcohol. TrimetUyletliylene. 

It boils at 36°, and unites directly with hydriodic acid, form- 
ing tertiary amyliodide, (Cff)''CI-CH^-CH^ boiling at 129°. 



HYDROCARBONS OF THE SERIES, C''h'^''~^ 575 

When bromine is poured into cooled amylene, the addition 
of each drop produces a hissing noise, indicating a violent reac- 
tion, and the product is a liquid amylene bromide, boiling be- 
tween 170 and 180°. If the operation be performed upon crude 
amylene, a mixture of several bromides will result. Trimethyl- 
ethylene yields a bromide containing (CH^)'=CBr-CHBr-CHl 

Isopropylethylene is formed by the action of alcoholic 
potassium hydrate on amyl iodide (Flavitzky). 

^g3>CH-CH2-CH2I — HI = g^3>CH-CH=CH2 
Amyl iodide. Isopropylethylene. 

This body also exists in small quantity in the mixture of 
hydrocarbons formed by the action of zinc chloride on amyl, 
alcohol. Boiling-point, 25°. It unites with hydriodic acid, 
forming a secondary iodide, (CH^)'=CH-CHI-CH^ which boils 
at 137-139°. It combines with bromine, forming the bromide 
(CH^)2=CH-CHBr-CH^Br, which boils between 180 and 190°. 

Propylethylene or Ethylallyl may be obtained by heating 

with sodium a mixture of allyl iodide and ethyl iodide. 

CH3-CH2I + CH2=CH-CH2I + Na2 = 2NaI + CH3-CH2-CH2-CH-CH2 
Ethyl iodide. Allyl iodide. Ethylallyl. 

It is also formed by the action of zinc ethyl on ethyl iodide. 
It boils at 37°, and combines with hydriodic acid, forming the 
iodide C^H^-CHI-CH^ boiling at 144°. It combines ener- 
getically with bromine, forming a bromide C^H^-CHBr-CH^Br, 
boiling at 175°. 

Polymerides of Amylene. — By the action of zinc chloride 
on amyl alcohol, there are formed, independently of amylene, 
other hydrocarbons, among which are the polymeric modifica- 
tions known as diamylene, C^^H^" ; triamylene, C^^H^" ; tetra- 
mylene, C^°H*° (Balard, Bauer). These bodies are formed by 
the union of two, three, or four molecules of amylene. 

HYDROCARBONS OF THE SERIES C^W^-\ 

Among the more simple hydrocarbons is one which was dis- 
covered by E. Davy, and which Berthelot has succeeded in 
preparing by various processes. It is acetylene, and is the 
first member of a series which includes, among others, the 
following hydrocarbons : 

Acetylene C2H2 (E. Davy, Berthelot). 

Allylene C^H* (Sawitsch). 

Crotonylene C*H^ (E. Caventou). 

Valerylene C^^ (Reboul). 



576 ELEMENTS OF MODERN CHEMISTRY. 

Acetylene, C^ff or CHeeCH. — This hydrocarbon is a prod- 
uct of the incomplete combustion of many organic substances, 
and is the only compound of hydrogen and carbon that has 
been obtained by direct union of these elements. 

According to Berthelot, it is formed when the electric arc 
is passed between carbon electrodes in an atmosphere of 
hydrogen. 

It may be obtained by heating ethylene bromide with an 
alcoholic solution of potassium hydroxide, thus : 

Cm'Br' + 2K0H = 2KBr + C^H'^ + 2ffO 

The most convenient mode of preparing acetylene is by 
the action of water upon calcium carbide, which is readily 
produced in the electrical furnace (Moissan) (page 327). 
C^Ca + 2H^0 = C^H^ + Ca(0H)2 

The reaction takes place at ordinary temperatures. 

Acetylene is a colorless gas, having a peculiar odor, sug- 
gesting that of garlic. At ordinary temperatures it dissolves 
in about its own volume of water. Its critical temperature 
is 37°. At 19.5° it is liquefied by a pressure of 39.8 atmos- 
pheres ; the resulting liquid boils at — 83°, and in evaporating 
absorbs enough heat to freeze a portion to a snow-like mass. 

Acetylene burns with a highly luminous and smoky flame. 
With 2.5 times its volume of oxygen, acetylene constitutes 
one of the most explosive gaseous mixtures. It combines 
directly with bromine, with which it yields a dibromide, 
C^H^Br^ and a tetrabromide, C^'H^Br*. 

When conducted into an ammoniacal solution of cuprous 
chloride, it produces a brownish red precipitate of cuprous 
acetylide. This reaction afi'ords a delicate test for acetylene, 
and an excellent means of removing it from gaseous mixtures. 
An analogous silver compound is similarly obtained. Both 
acetylides are highly explosive in the dry state ; with hydro- 
chloric acid they yield acetylene and the metallic chlorides. 
C^H^Cu^O -J- 2HC1 = Cu^CP + C^H'^ + H^O 

On account of its superior illuminating power, acetylene 
is now manufactured as a substitute for the ordinary gas 
from bituminous coal. 

Allylene, C^H*, the second member of the acetylene series, 
exists in two isomeric forms, methylacetylene^ CH^-C^H, a 
gas which resembles acetylene in its general properties and 
forms a precipitate when passed into solution of silver nitrate, 



GLYCOLS. ST*? 

and symmetrical allylene, CH^-C=CH2, whicli forms no pre- 
cipitate with silver nitrate. 

The number of isomers increases rapidly in this series as 
the molecules contain a greater number of carbon atoms. 



DIHYDRIC ALCOHOLS, OR GLYCOLS. 

The name glycols was given by Wurtz to the hydroxides of 
the series of hydrocarbons, C"H^'^. If ordinary alcohol be 
ethyl hydroxide, ordinary glycol is ethylene hydroxide. 

Ethyl hydroxide. Ethylene hydroxide. 

While alcohol reacts with a single molecule of a monobasic 
acid to form a neutral ether, glycol can react with either one 
or two molecules of a monobasic acid, thus forming two ethers. 
In other words, while the monohydric alcohols contain but one 
atom of hydrogen which is replaceable by a single radical of a 
monobasic acid, glycol contains in the two groups OH two such 
atoms of hydrogen, capable of being replaced by two radicals 
of a monobasic acid, or one radical of a dibasic acid. 

Ethyl acetate. Ethylene;diacetate. Ethylene succinate. 

The glycols yield diatomic acids by oxidation. 
There are isomeric glycols, or isoglycols, corresponding to the 
isoalcohols which have already been defined (page 521). 

A number of glycols of the series CH^'^+^O^ are now known. 

DENSITY AT 0°. BOILING-POINTS. 

Ethylene glycol, or glycol . . . C^WO"^ 1.125 197.5° 

Propylene glycol, or propylglycol . C^n^O"^ 1.051 188-189° 

Butylene glycol, or butylglycol . C^HiOQ'-^ 1.048 183-184° 

Amylene glycol, or amylglycol . . Q^W^O"^ 0.987 177° 

It is to be remarked that all of the members of the above 
series are not, strictly speaking, homologous. 

The isomerism of the glycols, like that of the alcohols, is 
due to the constitutions of their molecules, which can contain, 
like the molecules of the alcohols, the following groups : 

The primary group -CH^.OH 
The secondary group =CH.OH 
The tertiary group =C.OH 
z mm 49 



578 ELEMENTS OF MODERN CHEMISTRTf. 

Thus, ethylene glycol is primary, since it contains two 
groups, CHIOH. 

The amylene glycol derived from trimethylethylene is at the 
same time secondary and tertiary. 

Pinacone, which has already been mentioned (page 558), is 
a tertiary glycol; it contains two groups =(C.OH). 

CH2.0H r^l> C.OH CHS^ 9'^^ 

CH2.0H CH3-CH.0H CH3^ ^'^^ 

Glycol. Amylene glycol. Pinacone. 

(Secondary and tertiary.) (Tertiary.) 

Among the mixed glycols, that is, those containing at the 
same time two different alcoholic groups, is ordinary propylene 
glycol, which is primary and secondary. 

CIP.OH CH3 

CH2 CH.OH 

CH2.0H CH2.0H 

Normal propylene glycol. Ordinary propylene glycol. 

(Primary.) (Primary and secondary.) 



GLYCOL, OR ETHYLENE ALCOHOL. 

C2H602 = C2H4(OH)2 

Wurtz first obtained glycol by causing either iodide or bro- 
mide of ethylene to react with silver acetate 

Silver acetate. Ethylene diacetate. 

and saponifying the resulting ethylene diacetate by potassium 
hydroxide. 

^2^3^-^|(C2H4)" + 2K0H ==: 2(C2H30.0K) + (C2H*)" | ^j[J 
Ethylene diacetate. Potassium acetate. Glycol. 

It is best prepared by Hiifner and Zoller's process, which 
consists in heating ethylene bromide with an aqueous solution 
of potassium carbonate, thus : 

C2H*Br2 + K2C03 + H20 = C2n4(OH)2 + 2KBr + C02 

188 grammes of ethylene bromide, 138 grammes of po- 
tassium carbonate, and 1 litre of water are introduced into a 
large flask connected with a reversed condenser, and the mix- 



GLYCOL. 579 

ture is boiled until all of the ethylene bromide has disappeared. 
The aqueous liquid is then concentrated on a water-bath, and 
alcohol is added to precipitate the potassium bromide ; the 
alcoholic liquid is then distilled. Alcohol and water first pass, 
and when the temperature rises above 150°, the liquid which 
condenses is nearly pure glycol. 

Properties. — G-lycol is a somewhat syrupy, colorless, and 
odorless liquid, having a sweet taste. It mixes with water and 
alcohol in all proportions, but is scarcely soluble in ether. It 
boils at 197.5°, and distils without alteration. 

Its analogy to alcohol, from which it differs bv containing 
one more atom of oxygen, is demonstrated by the following 
experiments : 

1. If platinum black be moistened with glycol and then 
rapidly plunged into a jar of oxygen, a brilliant incandes- 
cence is manifested immediately, due to the energetic absorp- 
tion of oxygen. 

With dilute glycol, the oxidation is slower, and glycollic acid 
is formed. 

CH2.0H CH2.0H 

CH2.0H + 02 = i^Q^Qjj + H20 
Glycol. Glycollic acid. 

2. If glycol be heated with ordinary nitric acid, torrents of 
red vapor are disengaged, and the liquid deposits crystals of 
oxalic acid on cooling. 

CH2.0H CO.OH 

iH2.0H +'^'= bo.On +2H20 
Glycol. Oxalic acid. 

3. When glycol is heated with potassium hydrate to 250°, 
pure hydrogen is disengaged and potassium oxalate is formed. 

C2JJ6Q2 _|_ 2K0H = C^O^K^ + 4.W 

Glycol. Potassium oxalate. 

These experiments establish between glycol and glycollic and 
oxalic acids, relations analogous to those which exist between 
alcohol and acetic acid. 

Ethylene Chlorhydrate, or Glycol Chlorhydrin. — When 
hydrochloric acid gas is passed into glycol, a neutral com- 
pound is formed which constitutes the monocMorhydrin of 
glycol, or ethylene chlorhydrate. 

C2H4<OH ^ HCl = C2H4<Op + H20 
Glycol. Ethylene chlorhydrate. 



580 ELEMENTS OF MOBERN CHEMISTRY. 

This compound is intermediate between glycol and ethylene 
chloride, which is the dichlorhydrin of glycol. 



C^H*<0| 


C2H4<gJ^ 


C2H4<g 


Glycol. 


Monochlorhydrin of 


Dichlorhydrin of glycol 




glycol. 


(ethylene chloride). 



Glycol chlorhydrin is also formed by the direct union of 
ethylene gas and hypochlorous acid (Carius). 

C^H^ + HCIO = C^H^CIO 

It is a colorless liquid, having a density of 1.24 at 8°. It 
boils at 130-131°. 

Ethylene hromhydrate^ or glycol hromliydrin, is formed 
under circumstances analogous to those which furnish the 
chlorhydrate. It is a thick, colorless liquid, boiling at 147°. 

Ethylene Mtrates. — By the reaction of ethylene brom- 
hydrate on silver nitrate, at ordinary temperatures or by the 

aid of gentle heat, ethylene mononitrate, C^H*<;^4j , is 

obtained as a colorless or slightly yellow liquid, which is sol- 
uble in water. Density at 11°, 1.31. 

NO^ 
Ethylene dinitrate, C^H*<^/-^'Tvn-/-v2, is formed by the action 

of ethylene bromide on an alcoholic solution of silver nitrate. 
It is a mobile, colorless liquid, insoluble in water. Density at 
8°, 1.4837. It explodes by percussion (Henry). 

Ethylene Acetates. — When glycol is heated with acetic 
acid, it is converted into acetic ethers. 

C'-^H*<Q^ + C2H30.0H = C2H*<Q^'^^^ + H20 

Acetic acid. Ethylene monacetate. 

C2H4<^| + 2(C2H30.0H) = C2H^<^_-gH30 + ^^'^ 
Acetic acid. Ethylene diacetate. 

Ethylene monacetate, or monacetic glycol, is a liquid mis- 
cible with water and alcohol, and boiling at 182°. 

Ethylene diacetate, or diacetic glycol, can be prepared by the 
reaction of ethylene iodide on silver acetate. It is a colorless 
liquid, soluble in 7 parts of water ; it boils at 186°. 

It is thus seen that two neutral ethereal compounds can be 
formed by the action of one and the same monobasic acid on 
glycol, while the monohydric alcohols would furnish but a 
single compound ether under the same circumstances. 



ETHYLENE OXIDE. 581 

ETHYLENE OXIDE. 

cm 

C2H40=0<i,jj2 

If an excess of potassium hydroxide be added to glycol 
chlorhydrin contained in a test-tube, and a gentle heat be 
applied, a brisk effervescence will take place, due to a dis- 
engagement of vapor which may be ignited at the mouth of 
the tube. 

At a low temperature, this vapor condenses to a colorless 
liquid, which is ethylene oxide. 

C^H^CIO = C^H^O + HCl 

Glycol chlorhydrin. Ethylene oxide. 

Ethylene oxide has the composition of glycol, less the ele- 
ments of one molecule of water. 

However, it cannot be obtained by direct dehydration of 
glycol, for when that body is distilled with zinc chloride, 
among other products, aldehyde, which is isomeric with ethyl- 
ene oxide, is obtained. 

Greene has obtained ethylene oxide by double decomposi- 
tion, by heating ethylene bromide with anhydrous sodium 
oxide. 

C^IPBr^ + Na^O :== C'H^O + 2NaBr 

Properties. — Ethylene oxide boils at 13.5°. It dissolves 
in all proportions in water, alcohol, and ether. Under the 
influence of sodium amalgam and water, it fixes hydrogen 
directly, being transformed into alcohol. 

C^H^O + H^ = C^H^O 

It combines directly with water at 100°, regenerating glycol. 
C^H^O + H^O = C^H«0^ 

It possesses basic properties. 

If equal volumes of hydrochloric gas and vapor of ethylene 
oxide be mixed over the mercury-trough (the mercury should 
be slightly warmed) the two gases will disappear ; they combine 
to form a liquid which is glycol chlorhydrin. 
C^H*0 -f HCl = C^H^CIO 

If liquid ethylene oxide be added to a cooled solution of 
magnesium chloride, an abundant precipitate of magnesium 
hydroxide will be formed in the course of a day, and the liquid 

49* 



582 ELEMENTS OF MODERN CHEMISTRY. 

will contain glycol chlorhydrin. Oxide of ethylene precipi- 
tates magnesia as would a powerful base (A. Wurtz). 

Bases Derived from Ethylene Oxide. — Oxide of ethylene 
combines with ammonia, yielding a series of bases, the hydrox- 
ethylenamines^ which are formed by the direct union of one, 
two, or three molecules of ethylene oxide with one molecule of 
ammonia. 

C2H4.0H) C2H4.0H^ C'''H4.0H) 

H \ N C2H4.0H \ N C2HiOH \ N 

hJ hJ C^H^.OHJ 

Hydroxethylenamine. Dihydroxethylenamine. Triliydroxethylenamine. 

These bases are also formed by the action of ammonia on 
ethylene chlorhydrin. 

PI C2H4.0H) 

02H4<5jj + NH3 = H ^ N + HCl 

When ethylene chlorhydrin is treated with trimethylamine, 
the bodies combine, forming a chloride. 

N(CH3)3 + C2H4<2H _ C2H*^H|j^(,j 

When this chloride is treated with water and silver oxide, 
it is converted into a hydroxide. 
C2H4.0H1 

Choline, or hilineurine. — This hydroxide is an energetic 
natural base which exists in the bile, and is also a product of the 
position of a complex substance, lecithine, which exists in the 
brain, in the nerves, and in the yolk of eggs. 

Sulphonal. — Analogous to the glycols are the diatomic 
hydrosulphides, of which the type is methylene mercaptan, 
CH'^(SH)^. The oxidation of these hydrosulphides yields 
disulphones, which may also be obtained by condensation from 
the alkyl hydrosulphides. Thus, when a mixture of ethyl- 
mercaptan with acetone is cautiously oxidized by means of 
potassium permanganate, condensation takes place and di- 
ethylsulphon-dimethylmethane is formed. 

2(C2H5.SH) + (CH3)2CO + 0* = (CH3)2C(S02.C2H5)2 + H20 
Ethyl hydrosulphide. Sulphonal. 

The latter is used under the name sulphonal as one of the 
most favored hypnotics. It is a colorless solid, crystallizing 
in prisms melting at 125°, and it boils at 300°. It is only 
slightly soluble in cold water. 



ACETAL. 583 

ACETAL. 

We may conceive of the existence of a glycol isomeric with 
that which has been described, and bearing the same relations 
to the latter that aldehyde has to ethylene oxide. 
CH2 ^ ^ CH3 

CH2 ^ CHO 

Ethylene oxide. Aldehyde. 

CH2.0H CH3 CC13 

CH2.0H CH< ^^ ^^^^OH 

Ethylene glycol. Ethylidene glycol. Chloral hydrate. 

Just as glycol is formed by the hydration of ethylene oxide, 
ethylidene glycol should be formed by the hydration of alde- 
hyde. Indeed, on contact with water aldehyde becomes heated, 
and doubtless is converted into the glycol in question, which 
is, however, too unstable to be isolated. In general, all com- 
pounds which contain two hydroxyl groups in combination 
with the same carbon atom are quite unstable, and readily 
decompose, giving up a molecule of water. It is so with 
chloral hydrate, which must be considered as a trichlor-deriva- 
tive of ethylidene glycol. The latter is at once resolved into 
aldehyde and water, but its methyl and ethyl derivatives are 
stable, and have long been known under the names dimethyl- 
acetal and acetal. 

Off CH^ 

Dimethylacetal. Acetal. 

Dimethylacetal is produced when a mixture of methyl and 
ethyl alcohols is oxidized by sulphuric acid and manganese 
dioxide. It boils at 64°, and much resembles acetal. 

Acetal. — This compound was discovered by Liebig. It 
exists in the more volatile portions of the product of the dis- 
tillation of crude alcohol. It is formed synthetically when 
alcohol is heated to 160° with aldehyde, and also by the action 
of sodium ethylate on monochlorether. 

^'^'<aC^H^ + C^^H^ONa = NaCl + C^H^<^^^g5 

Monochlorether. Acetal. 

It is found among the products of the oxidation of alcohol. 

Properties. — Acetal is a liquid, having a peculiar, agreeable 
odor, insoluble in water. Its density at 20° is 0.821. It 
boils at 104°. 



584 ELEMENTS OF MODERN CHEMISTRY. 



ETHYLENE-DIAMINES. 

These bases result from the substitution of one, two, or 
three ethylene groups, (C-H*)'', each for two atoms of hy- 
drogen in two molecules of ammonia, and are formed by the 
action of alcoholic ammonia on ethylene bromide at ordinary 
temperatures. 

C2H4Br2 + 2NH3 = C2H*(NH2)2.2HBr 
Ethylene-diamine 
hydrobromide, 

CH2-NH2 f (cm^)" 

Ethylene-diamine, ^jj2_j^jj2 ^^^ ] ^^ i^ ^ liquid base, 

boiling at 116.5°, and melts at 8.5°. By the prolonged action 
of an excess of ethylene bromide, it is converted successively 
into diethylene-diamine and triethylene-diamine. 

r(C2H*)" r(C2H4)'' f(C2H4)" 

N2Jh2 w\{Qm^)" wlicm^)" 

(H2 (H2 UC2H*)" 

Ethylene-diamine. Diethylene-diamine. Ti-iethylene-diamine. 

Diethylene-diamine, or piperazine, forms tetragonal crystals 
which melt at 104°. It boils without decomposition at 146°. 
The ethylene-diamines are diacid^ that is, they combine with 
two molecules of a monobasic acid, such as hydrochloric or 
hydrobromic acid (Hofmann). 

Tetramethylene diamine (p^ifrescine), NH^-CH^-CH^- 
CH^-CH^-NH'^, and Pentamethylene diamine (cadaverine), 
NH^-(CH^)^-NH'^, are ptomaines formed during the putre- 
faction of animal matters. Ladenburg has synthesized them. 

ISETHIONIC ACID. 

C2H6SO* = C21I^<^H^^ 

Oxide of ethylene unites directly with sodium acid-sulphite 
(bisulphite), forming sodium isethionate. 

C2HiO + ^^>S03 = C2H4<gH^^ 

Sodium isethionate. 

The same salt is formed when ethylene chlorhydrin is heated 
with neutral sodium sulphite. 

Qm^<^f + Na2S03 = C2H4<g^3j^^ + NaCl. 



TAURINE. 585 

Isethionic acid is prepared by the action of sulphuric anhy- 
dride upon alcohol or ether. The product is diluted with 
water, boiled for some time, and then neutralized with barium 
carbonate. The liquid is filtered and the filtrate decomposed 
exactly with sulphuric acid : isethionic acid remains in solution. 

Isethionic acid is a sour liquid which solidifies to a crys- 
talline mass on long standing over sulphuric acid. Its salts 
are very stable. It is isomeric with ethylsulphuric acid. 
Phosphorus pentachloride transforms it into a chloride. 

C2H*<^j2.0K + ^^^^^ = ^'^*<S02.Cl + ^^^ + ^^^ + ^^^^'^ 

Potassium isetliionate. Chlorethylsulphonic 

chloride. 

The latter is a liquid, boiling at 120° ; it is decomposed by 
water at 100°, into chlorethylsulphonic and hydrochloric acids. 

Chlorethylsulphonic acid. 



TAURINE. 

This important acid, whose existence in the bile was dis- 
covered by Grmelin in 1824, is related to isethionic acid; it is 
amido-isethionic acid, that is, it is derived from the latter acid 
by the substitution of a group NH^ for a group OH. It may 
be obtained by synthesis by the action of ammonia on chlor- 
ethylsulphonic acid or on silver chlorethylsulphonate. The 
following formulae indicate the relations between isethionic 
and chlorethylsulphonic acids and taurine : 

C^H'<^0^,,OH C'H.<«,ojj' C2H*<^H;;^jj 

Isethiouic acid. Chlorethylsulphonic acid. Taurine. 

Taurine crystallizes in large, brilliant, oblique rhombic prisms, 
very soluble in boiling water and but slightly soluble in cold 
water. When the crystals are heated they melt, and decompose 
at an elevated temperature. 

Strecker has obtained an isomeride of taurine by heating 
ammonium isethionate. 

Ammonium isethionate. Isethionamide. 



586 ELEMENTS OF MODERN CHEMISTRY. 

PKOPYLENE GILYCOLS. 

C3H6(OH)2 

Normal propylene glycol (page 577) has been obtained from 
normal propylene bromide (page 573). This bromide is mixed 
with acetic acid and heated with silver acetate : propylene di- 
acetate is formed, 0^11*^(0^11^0^)^, and separated by distillation, 
after which it is decomposed by a quantity of dry potassium 
hydroxide just sufficient to remove its acetic acid. 

Normal propylene glycol is a colorless, syrupy liquid, boil- 
ing at 216°, and having a density of 1.0652 at 0°. It is 
miscible with water and alcohol in all proportions. When 
oxidized, it yields hydracrylic acid (Geromont, Keboul). 

Ordinary propylene glycol is prepared from ordinary prop- 
ylene bromide by the same process indicated above. It is a thick, 
colorless liquid, having a density of 1.051 at 0°. It boils at 
188-189°. When diluted with water and mixed with plati- 
num black, it absorbs oxygen, and is converted into lactic acid 
(A. Wurtz). 

aLYOEROL (GLYOERIN). 

C3H803 = C3H5(OH)3 

Grlycerol was discovered by Scheele in 1779, and studied 
by Ohevreul, Pelouze, and especially by Berthelot, who de- 
monstrated its character of a trihydric alcohol. 

Pelouze and Gelis realized the first artificial formation of 
a fatty body by passing hydrochloric acid gas into a mixture 
of butyric acid and glycerol : butyrin was thus produced. 

Preparation. — Glycerol is an accessory product in the man- 
ufacture of lead plaster. When the preparation of that sub- 
stance is terminated, the water is decanted from the lead soap 
which separates, and hydrogen sulphide is passed through 
the liquid in order to precipitate as sulphide any traces of lead 
that may be dissolved. It is then filtered and evaporated on a 
water-bath. The glycerol remains as a colorless, syrupy liquid. 

It is obtained in large quantities in the arts as an accessory 
product in the manufacture of stearin candles. 

Properties. — Glycerol is a colorless liquid, having a syrupy 
consistence and a sweet taste. Its density at 15° is 1.28. It 
dissolves in all proportions in water and alcohol, but is almost 
insoluble in ether. When quickly heated, it distils between 
275 and 280° 3 and it may be readily distilled in a vacuum. 



ETHERS OF GLYCEROL. 587 

Pure glycerol is crystallizable, and solidifies below 0°, but 
solid glycerol melts only at 17°. 

When subjected to the action of dilute nitric acid, glycerol 
is converted into a triatomic acid, which is called glyceric 
acid (Debus, SocolofF). 

C^H^O^ + 0' = H^O + C^^H^O* 

Glycerol. Glyceric acid. 

When heated with phosphorus iodide, P'^P, glycerol is con- 
verted into allyl iodide (Berth elot and de Luca) (page 529). 

ETHERS OF GLYCEROL. 

G-lycerol, C^H^(OH)^, which contains three groups OH, can 
form three classes of ethers by the substitution of one, two, or 
three monobasic acid radicals for as many atoms of hydrogen 
in these hydroxyl groups. If acetic acid be heated with 
glycerol, according to the proportions of the mixture, three 
different acetic ethers of glycerol may be obtained, ethers 
which Berthelot has designated as acetins. 

n, rO.C2H30 „, fO.C2H30 uf ro.C2H3o 

C3H5^0H C3H5Jo.C2H30 C3H5J 0.C2H30 

(oh (oh (o.c^hsq 

Monacetin. Diacetin. Triacetin, 

In the same manner, by the action of the hydracids upon 
glycerol, neutral combinations are formed, analogous to the 
chlorides of the radicals C°H^'^+', as well as to the dichloride 
of ethylene and to ethylene chlorhydrate. These compounds 
are formed by the substitution of one, two, or three atoms of 
chlorine or bromine for as many hydroxyl groups in glycerol. 
,„ fci /,/ rci 

C3H5^ oh C3H5^CI 

(oh [oh 

Monochlorhydrin. Dichlorhydrin. 

Chlorine Ethers of Glycerol, or Chlorhydrins. — There 
are two monochlorhydrins, two dichlorhydrins, and one tri- 
chlorhydrin. 

Monochlorhydrins. — The two monochlorhydrins have been 
studied by Hanriot, and difi'er by the position of the chlorine 
atom. 

CH2.C1 CH2 oh 

CH.OH CH.Cl 

CH2.0H CH2.0H 

a monochlorhydrin, j8 monochlorhydrin. 



588 ELEMENTS OP MODERN CHEMISTRY. 

a monochlorliydrin, obtained by Bertbelot by tbe action 
of hydrocbloric acid on glycerol, is a thick, colorless liquid, 
soluble in water, alcohol, and ether, and boils at 213° (Han- 
riot). Density, 1.338. /? monochlorhydrin has been obtained 
by the direct union of hypochlorous acid and allyl alcohol. 
CH2 CH2.0H 

CH + HCIO = CH.Cl 

CH2.0H CH2.0H 

Its density at 13° is 1.328, and it boils at 230-235°. 
Dichlorhydrms. — The isomerism of the dichlorhydrins is 
analogous to that of the monochlorhydrins. 



CH2.C1 


CH2.0H 


CH.OH 


CH.Cl 


CH2.C1 
a dichlorhydrin. 


CH2.C1 
^ dichlorhydrin. 



Both are formed, the first in larger quantity, when glycerol 
is heated with a large excess of hydrochloric acid. 

Pure a dichlorhydrin is prepared by treating epichlorhydrin 
(see farther on) with hydrochloric acid. 

CH2.C1 CH2.C1 

CH ^ + HCl = CH.OH 

CH2^ CH2.C1 

Epichlorhydrin. a dichlorhydrin. 

It is a liquid of an ethereal odor, slightly soluble in water. 
Its density at 0° is 1.3835, and it boils at 172-173°. When 
heated with a large excess of hydriodic acid, it is converted 
into isopropyl iodide. 

/5 dichlorhydrin is formed by the action of chlorine on allyl 
alcohol, or that of hypochlorous acid on allyl chloride. 



CH2 


CH2.0H 


CH + HCIO 


- CH.Cl 


CH2.C1 
Allyl chloride. 


CH2.C1 
^ dichlorhydrin. 



Its density at 0° is 1.371, and it boils at 182-183°. Con- 
centrated caustic potash converts it, like its isomeride, into 
epichlorhydrin. 

Trichlorhy drill. — When dichlorhydrin is heated with phos- 



ETHERS OF GLYCEROL. 580 

phorus pentachloride, the last hydroxyl group is replaced by 
chlorine ; trichlorhydrin is thus obtained (Berthelot). 

rci rci 

C3H5^ Cl + PC15 = C3H5 J CI + P0C13 + HCl 

(oh (Cl 

Dichlorhydrin. Tricblorhydrin. 

It is a liquid, boiling at about 155°. 

Ejpichlorliy drill. — When dichlorhydrin is treated with a con- 
centrated solution of caustic potash, the elements of hydro- 
chloric acid are removed, and a body is obtained which Berthe- 
lot has named epichlorhydrin. 

CH2C1 
C3H5C12(OH) — HCl = C3H5C10 = CH ^^ 

Dichlorhydrin. Epichlorhydrin. 

Epichlorhydrin is a mobile liquid, heavier than water, and 
having an agreeable, ethereal odor. Its taste is at first sweet, 
afterwards sharp and burning. It boils at 118-119°. It is 
soluble in all proportions in alcohol and ether, but not in 
water. 

It combines directly with hydrochloric acid, regenerating 
dichlorhydrin. When heated for a long time with water, it 
combines with one molecule of that liquid, forming mono- 
chlorhydrin. 

O^H^CIO + H^O = C^H^C1(0H)2 

Tribromhydrin, or Propenyl Tribromide, C^H^Br^ = 
CH^Br-CHBr-CH'^Br.— This is obtained by adding 1.5 parts 
of bromine to one part of cooled allyl iodide. Iodine sepa- 
rates, and the liquid is washed with potassium hydrate and 
distilled. 

C^H^I + 3Br = C^H^Br^ + I 

Tribromhydrin crystallizes in brilliant colorless prisms, 
fusible at 16°. It boils at 219-220°. 

Glycide. — When a monochlorhydrin is treated with baryta 
and anhydrous ether, it loses the elements of hydrochloric acid, 
and is converted into glycide (Hanriot). 

CH2.C1 ^^^->0 

^ HCl 



CH.OH 


CH''^ 


CH2.0H 

Monochlorliydrin. 


cn2.0H 

Glycide. 

50 



590 ELEMENTS OF MODERN CHEMISTRY. 

Glycide is a mobile liquid, boiling at 157°. Its density at 
0^ is 1.165. Water dissolves it, regenerating glycerol. 

C^H^O.OH + H^O = C^H^OH)^ 

Trinitroglycerol, or Propenyl Trinitrate. — When glyce- 
rol is poured drop by drop into a mixture of concentrated nitric 
and sulphuric acids, cooled in a vessel of cold water, oily drops 
of trmitroglycerol^ C"H^(0-NO^)^, are precipitated. It is a 
colorless oil, insoluble in water, and explodes with great vio- 
lence by percussion, by heat, or, when impure, even sponta- 
neously. 

On account of this property, nitroglycerin is employed as an 
explosive ; but it is generally incorporated with inert matter, 
such as finely-divided silica. Such mixtures are called dyna- 
mites. The manufacture of nitroglycerin is usually conducted in 
wooden structures which are partly underground, and removed 
from exposure to influences which might cause the explosion 
of the product. The explosive force of the compound is more 
than six times as great as that of an equal quantity of gun- 
powder, and nitroglycerin produces effects equal to those of 
powder with an economy of about thirty per cent. Its explosion 
is too violent to permit its use in fire-arms, but it is well adapted 
to blasting operations. Curiously enough, while a drop of nitro- 
glycerin placed on an anvil and struck with a hammer explodes 
with a loud report, the same drop would burn quietly if brought 
into a flame. 

Other Glycerol Ethers. — Berthelot has obtained a number 
of glycerol ethers by directly heating glycerol with acids. 
When the reaction is terminated (it is often very slow), he sat- 
urates the excess of acid with calcium hydrate, and extracts 
the neutral fatty body, that is, the ether of glycerol, with 
ether. In this manner he has formed a certain number of 
natural fatty bodies by combining their acids with glycerol. 



NATURAL FATTY BODIES. 

The fats encountered in nature are glycerides, that is, ethers 
of glycerol. The memorable researches of Chevreul have 
shown that when these fats are methodically treated with 
different solvents, various immediate principles are separated, 
of which the most common are stearin, palmitin, and olein. 



NATURAL FATTY BODIES. 591 

They are the tristearic^ tripalmitic^ and trioleic ethers of 
glycerol. 

r O.C18H350 r O.C16H310 r o.cishsso 

C3H5 J O.C18H350 C3H5i O.C16H310 C3H5J O.C18H330 

[ O.C18H350 { O.C16H310 ( O.C18H330 

stearin. Palmitin. Olein. 

When these glycerol ethers are subjected to the action of 
alkalies, lime, or oxide of lead, in presence of boiling water, 
they are decomposed, absorbing at the same time the elements 
of water : glycerol and the acid are set free, and the latter 
combines with the base forming a soap (see page 593). Thus, 
when stearin is boiled with milk of lime, calcium stearate and 
glycerol are formed. When olein is heated with water and 
litharge, it yields lead oleate and glycerol. 

Most of the fats and oils occurring in nature consist of such 
glycerides mixed in various proportions, and may be resolved 
into the respective acids and glycerol. 

Stearin and palmitin are solids, olein is liquid. In the 
fats, the solid principles predominate ; the oils contain a 
larger proportion of olein. 

Steariyi is extracted from tallow. That substance is dissolved 
in boiling ether and made to crystallize. The crystals are 
pressed, and the operation is repeated with them many times 
until a substance is obtained which crystallizes in brilliant little 
scales, fusible at 66.5°. They are but slightly soluble in alco- 
hol and in cold ether, but freely soluble in boiling ether. 

Palmitin has been extracted, by the aid of boiling alcohol, 
from palm-oil which has previously been submitted to heavy 
pressure between sheets of porous paper. It melts at 60° 
(Heintz). 

Olein is the predominating principle of olive-oil and almond- 
oil, from which it is difficult to obtain it in a pure state. Ber- 
thelot has prepared triolein artificially by heating glycerol to 
a temperature between 200 and 240° with an excess of oleic 
acid. The mass thus obtained is treated with lime and ether ; 
the latter dissolves the triolein and leaves calcium oleate. 
The ethereal solution is decolorized with animal charcoal and 
mixed with eight times its volume of alcohol, which precip- 
itates the triolein. When dried in a vacuum, triolein is an oil 
which solidifies at — 6°. Its density* is between 0.90 and 0.92. 
It is insoluble in water, and very slightly soluble in alcohol. 

In contact with mercuric nitrate or with peroxide of nitrogen 
(red vapors), olein is converted into a crystalline, solid, fatty 



592 ELEMENTS OF MODERN CHEMISTRY. 

body, fusible at 36°, to wbicb Boudet has given the name 
elaidin. 

Fat Oils and Drying Oils. — The oils of olives, sweet 
almonds, rape-seed, beech-nuts, etc., acquire an acrid taste and 
a disagreeable odor when they are long exposed to the air, but 
they do not solidify. They are called fat^ or non-siccative 
oils. 

Olive-oil is the type of this class. It is extracted by press- 
ure from crushed olives, and has a greenish-yellow color ; its 
taste is sweet and agreeable ; it is odorless. At a temperature 
a few degrees above 0°, it becomes a solid mass. When agitated 
with mercurous nitrate, it becomes solid, the olein which it 
contains being transformed into elaidin. It becomes rancid by 
exposure to the air. 

When other oils, such as linseed, walnut, hemp-seed, poppy 
and castor oils are exposed to the air, they thicken and finally 
are converted into somewhat elastic, yellow, transparent masses, 
species of soft varnishes. They are, therefore, called drying 
oils, and are employed in the preparation of paints and varnishes. 

The changes which oils undergo on contact with the air are 
caused by an absorption of oxygen, and are accompanied by a 
disengagement of more or less carbon dioxide. Every one is 
familiar with the uses of the natural fatty bodies in the arts 
and in domestic economy. Among the industrial applications, 
we can only mention the employment of tallow and palm-oil in 
the manufacture of candles, and of these as well as other 
oils and fats in soap-making. 

Stearin Candles. — To convert tallow into stearin candles, it 
is saponified by lime, that is, it is first converted into a lime 
soap, which is then decomposed by sulphuric acid. The latter 
acid causes the fatty acids to separate, and they solidify on 
cooling. They are strongly compressed, first between warm, 
and finally between hot plates, so that the oleic acid is ex- 
pressed, while the fatty acids proper remain. This process, 
which was invented by de Milly and Motard in 1829, consists, 
as may be seen, in entirely saponifying the tallow by lime. In 
1854, de Milly modified it by considerably reducing the amount 
of lime, and consequently the proportion of sulphuric acid 
required. But it is then .necessary to operate at higher tem- 
peratures by the aid of superheated steam. The operation is 
conducted in closed vessels, and with 2.5 parts of lime, 100 
parts of tallow may be saponified at a temperature of 170 or 
180°.. 



SOAP. 593 

Palm-oil may be converted into candles by a still more 
simple process, whicb consists in subjecting it to tbe action 
of superheated steam at 300°. It is thus directly decom- 
posed into fatty acids and glycerol, for the vapor of water, 
at the high temperature employed, acts precisely as would an 
alkali. 

Soaps. — In the south of Europe, and principally at Mar- 
seilles, oils of inferior quality are used for the manufacture of 
soap, and the oils of sesame and earth-nut have been employed 
for this purpose for some years. These oils are saponified by 
boiling them in large boilers with a weak solution of caustic 
soda. The oil thus becomes pasty, the excess of oil making an 
emulsion with the solution of soap which is first formed. 
More concentrated soda lye containing common salt is then 
added, and the saponification is finished by boiling ; the soap, 
which is insoluble in the concentrated lye, comes to the surface 
of the liquid, and the lye is then drawn off. When the soap 
is well made, the paste hardens on cooling ; it has a bluish-gTay 
color, due to a ferruginous soap mixed with sulphide of iron. 
The iron and sulphur are derived from the materials employed, 
crude caustic soda containing a small quantity of iron. If this 
paste be heated with about one-twelfth its weight of water, or 
a very weak solution of caustic soda, it melts, and if the mass 
be allowed to stand undisturbed, it wiU separate into two por- 
tions, the lower and strongly-colored layer containing the more 
dense ferruginous soap ; the upper layer constitutes white soap. 
When the latter is completely clarified by the deposit of the 
ferruginous soap, it is di-awn off into large moulds, where it solid- 
ifies. White soap is thus obtained. If, on the contrary, mar- 
bled soap be desired, the paste is frequently agitated during the 
cooling. The colored part, that is, the ferruginous soap, thus be- 
comes diffused throughout the whole mass, forming bluish veins. 

For some years, large quantities of soap have been prepared 
by combining with caustic soda the oleic acid obtained as an 
accessory product in the manufacture of stearin candles. 

Soft soaps have potash for their base. They are manufact- 
ured from various oils, such as hemp, poppy, and linseed oils, 
which are saponified by caustic potash lye. 

Saponification. — It will have been noticed that all of these 

industrial operations have for their object the decomposition 

of neutral fats into fatty acids, either free or combined with 

a base. This decomposition has received the name saponifi- 

nn 50* 



594 



ELEMENTS OP MODERN CHEMISTRY. 



cation. It may be effected by tbe action of water and heat 
alone, by the action of a base, or by the action of a powerful 
acid, such as sulphuric acid (sulphuric saponification). In the 
latter case, the acid acts upon the glycerol, forming a sulpho- 
glyceric acid. Whatever process be employed to effect this 
decomposition, the presence of water is always necessary, for 
the elements of that liquid combine directly with the fatty 
body which is decomposed, as Chevreul has very well shown. 
In this respect, the decomposition of palmitin by superheated 
steam may serve as a type for all reactions of this class. 
ro.ci6H3io roH 

Cm^\ O.C16H310 + 3H20 = Cm^\ OH + 3Ci6H3iO.OH 
( O.C16H310 I OH 

Palmitia. Glycerol. Palmitic acid. 



POLYATOMIC AND POLYBASIC ACIDS. 

These acids are related to the polyhydric alcohols, just as 
the acids containing two atoms of oxygen, and which we have 
already studied, are related to the monohydric alcohols. 

The polyatomic acids are classed in several series, among 
which we must consider in a special manner those which in- 
clude glycollic and oxalic acids. As we have already seen, 
these two acids are products of the direct oxidation of glycol. 

Their homologues are related to the higher glycols. 



Glycols. 


Acids, CnH2n03. 


Acids, CnH2ci-'-!0 


CH2.0H 


CH2.0H 


CO.OH 


CH2.0H 


CO.OH 


CO.OH 


Glycol. 


Glycollic acid. 


Oxalic acid. 


CH2.0H 


CH2.0H 


CO.OH 


CH2 


CH2 


CH2 


CH2.0H 


CO.OH 


CO.OH 


Normal propylglycol. 


Hydracrylic acid. 


Malonic acid. 


CH3 


CH3 




CH.OH 


CH.OH 




CH2.0H 


CO.OH 




Isopropylglycol. Lactic acid ot fermentation. 




CH2.0H 




CO.OH 


CH2 




CH2 


CH2 




CH^ 


CH2.0H 




CO.OH 


Normal butylglycol. 




Succinic acid. 



GLYCOLLIC ACID, GLYOXYLIC ACID, AND GLYOXAL. 595 

The first of tlie above series is that of glycol and the higher 
glycols. Among the latter, the true homologues of glycol 
would be those which differ from the latter by nCH^, and of 
which the formulas would consequently be analogous to that 
of normal propylglycol. Ordinary propylglycol, which yields 
lactic acid by oxidation, is an isomeride of normal propylglycol. 

The second series is that of glycollic acid and its homologues. 
They are derived from the corresponding glycols by the sub- 
stitution of for H^ in one group, CHI OH They conse- 
quently contain but one carboxyl group, CO. OH ; they are 
monobasic, for the hydrogen atom of the last group can be 
replaced by a metal. It will also be noticed that they are at 
the same time acids and alcohols, — acids by virtue of the carb- 
oxyl, CO.OH, primary alcohols by virtue of the group CH^OH, 
or secondary alcohols by virtue of the group CH.OH. 

The third series is that of oxalic acid and its homologues. 
They are derived from the glycols by substitution of 0^ for 
2W in two groups, CH^OH. They consequently contain two 
carboxyl groups, CO.OH, and they are dibasic because the 
H of each of these groups may be replaced by an equivalent 
quantity of metal. 

Between glycollic and oxalic acids there exists a remarkable 
acid, because it is at the same time a monobasic acid and an 
aldehyde : it is glyoxylic acid. It contains C^H^O*, one more 
atom of oxygen than oxalic aldehyde, which is called glyoxal, 
C^H^O^ and two atoms of hydrogen less than glycollic acid. 
These relations of composition will be clearly seen from the fol- 
lowing formulas : 

CH2.0H CHO CHO CO.OH 

CO.OH CO.OH CHO CO.OH 

Glycollic acid. Glyoxylic acid. Glyoxal. Oxalic acid. 



GLYCOLLIC ACID, GLYOXYLIC ACID, AND 
GLYOXAL. 

Glycollic Acid, CHXOH)-COOH.— This acid is formed 
by the oxidation of glycol, but is best prepared by heating 
potassium monochloracetate with dilute potassium hydroxide. 

KC^H^CIO^ + KOH = KCl + KC^ffO^ 

Potassium monochloracetate. Potassium glycollate. 



596 ELEMENTS OF MODERN CHEMISTRY. 

The acid forms deliquescent crystals, very soluble in water, 
alcohol, and ether. It has a strong acid reaction. When 
heated, it loses the elements of water, and is converted into 
glycollide^ or glycolUc anhydride, C^H^O^, or C*H*0*. 

Glyoxylic Acid, CHO-COOH. — When fuming nitric acid, 
water, and 80 per cent, alcohol are carefully superposed in 
layers in a tall jar, and left for some days at ordinary tem- 
peratures, mixture takes place by diffusion, and the products 
of this slow oxidation of the alcohol are glycollic acid, gly- 
oxylic acid, and glyoxal. When the carefully evaporated 
liquid is neutralized with chalk, calcium salts of the two acids 
are formed and may be precipitated by the addition of alco- 
hol, in which they are insoluble. From an aqueous solution 
of the two salts the glyoxylate deposits first on spontaneous 
evaporation. The free acids may be obtained by decomposing 
the calcium salts with oxalic acid. Glyoxylic acid is also 
formed by the careful oxidation of glycol. 

Grlyoxylic acid is a syrupy and very acid liquid. It has 
the properties of an acid and those of an aldehyde, as is 
indicated by its formula. Its solution reduces ammoniacal 
silver nitrate. When heated with sulphuric acid it disen- 
gages carbon monoxide. 

02JJ2O3 ^ 2C0 + H^O 

Nascent hydrogen converts it into glycollic acid. 

Glyoxal, CHO-CHO, may be obtained from the alcoholic 
liquid above mentioned, from which calcium glycoUate and 
glyoxylate have been precipitated. 

It is a deliquescent, amorphous solid, slightly colored, and 
very soluble in water and alcohol. Its aqueous solution 
energetically reduces ammonio-nitrate of silver. Like other 
aldehydes, glyoxal combines with sodium acid-sulphite, with 
phenylhydrazine, and with hydroxylamine. With the latter 
it forms the compound HO.N=CH-CH=N.OH, gJyoxime, 
which is the type of a dioxime. Glyoxal is the aldehyde 
corresponding to oxalic acid. 

CHO CO.OH 

CHO CO.OH 

Glyoxal. Oxalic acid. 



LACTIC AND PARALACTIC ACIDS. 597 



LACTIC AND PARALACTIC ACIDS. 

[a-OXYPROPIONIO ACID.] 
C3H«03 = CH3-CH(0H)-C0.0H 

Formation and Constitution. — Lactic acid was discovered 
by Scheele in sour milk. Berzelius discovered the existence in 
various liquids of the animal economy of an acid which was at 
first believed to be identical with that which results from the 
acid fermentation of milk. Later, an acid identical with the 
latter was found in various vegetable juices, and was recog- 
nized to be the product of a peculiar fermentation of glucose, 
called the lactic fermentation (see page 647). It was also 
discovered that the lactic acid of fermentation is not identical 
with that which exists in the animal liquids, especially that 
liquid which impregnates the muscular fibres. The latter 
acid is called paralactic or dextrolactic acid. It rotates the 
plane of polarized light to the right, and its salts differ in cer- 
tain properties from those of ordinary lactic acid. Wislicenus, 
who has most carefully investigated this isomerism, believes 
it to be caused by a different arrangement of the atoms in 
space, and the results of many researches tend to confirm this 
view. Such cases of isomerism which cannot be represented 
by the ordinary structural formula are classed as stereoisomer- 
ism^ and will be more fully explained farther on (see Tartaric 
Acid). An acid of the same chemical properties, but turning 
the plane of polarization to the left, has recently been discov- 
ered by Schardinger. It is distinguished as levolactic acid. 

Independently of these stereoisomeric lactic acids, there is 
another isomer which was at first named ethyleue-lactic acid, 
and which results from the oxidation of normal propylglycol ; 
its constitution is expressed by the formula 
CH2.0H 
CH2 
io.OH 

It is Tiydracrylic add; it is also formed when /9-iodopropi- 
onic acid is treated with water and silver oxide. Its character- 
istic property is its easy decomposition into water and acrylic 
acid, hence the name hydracrylic (Wislicenus). 

Its isomeride, lactic acid of fermentation, is formed by the 
oxidation of ordinary propylglycol (A. Wurtz). This fact 



598 ELEMENTS OF MODERN CHEMISTRY. 

determines its constitution, whicli can also be deduced from 
a very interesting mode of formation discovered by Strecker. 
When a mixture of aldehyde, hydrocyanic acid, and hydro- 
chloric acid is allowed to stand for some time, ammonium chlo- 
ride and lactic acid are formed. 

CH3 
V + CNH + HCl + 2H20 = NH4C1 -1- CH.OH 

™0 fco.OH 

Aldehyde. Hydrocyanic Lactic acid, 

acid. 

The isomerism of lactic and hydracrylic acids may be readily 
understood by the aid of the following formulae : 
CH2.0H CH3 

CH2 CH.OH 

CO.OH CO.OH 

Hydracrylic acid. Lactic acid. 

Both acids are monobasic ; each contains the group CO.OH, 
which is characteristic of organic acids. The third oxygen 
atom exists in alcoholic hydroxyl, either in the primary group 
CHI OH, or in the secondary group CH.OH. 

The preceding formulae show that lactic acid has a mixed 
function ; it is at the same time an alcohol and an acid. This 
is made evident in all of its compounds, and it will be sufficient 
to mention that one molecule of lactic acid in its function as 
an acid^ can react with and etherify another molecule in its 
function of an alcohol, the hydroxyl of the group CO.OH 
forming a molecule of water with the hydrogen of the alco- 
holic hydroxyl in the second molecule of the acid. The 
dilactic acid, lactic anhydride, and lactide which are formed by 
the more or less complete dehydration of two molecules of 
lactic acid, are veritable dilactic ethers. This point has been 
developed by Grimaux. 

Preparation of Lactic Acid. — A mixture of 3 kilo- 
grammes of glucose dissolved in 13 litres of water, 4 kilo- 
grammes of sour milk, 100 grammes of old cheese, and 1.5 
kilogrammes of pulverized chalk, is exposed to a temperature 
of 30 or 35°. At the end of a week, the whole solidifies to 
a mass of calcium lactate. The salt is purified by crystal- 
lization, and is exactly decomposed by dilute sulphuric acid. 
The calcium sulphate is separated by filtration, and the acid 
liquid is boiled and saturated with hydrocarbonate of zinc; 



LACTIC AND PARALAOTIC ACIDS. 599 

It is then filtered and allowed to cool. The zinc lactate crys- 
tallizes, and its solution being decomposed by hydrogen sul- 
phide, zinc sulphide and lactic acid are obtained. The filtered 
solution is evaporated on a water-bath. 

For the preparation of lactic acid on a smaller scale, advan- 
tage is taken of the fact that some sugars (glucose, fructose) 
upon heating with alkalies yield considerable quantities of 
the acid. 

Properties. — Lactic acid is generally obtained as a color- 
less, syrupy liquid, having a decided acid taste. In the pure 
state it forms hard crystals, which melt at 18°. When heated, 
it begins to lose water at 130°, and is converted, little by little, 
into a yellow, amorphous mass, insoluble in water, but soluble 
in alcohol and ether. This body is dilactic acid, C^H^°0^. 

At 230°, it disengages a small quantity of carbon monoxide 
and carbon dioxide, and a product distils which often solidifies 
on cooling. It is lactide, or dilactic anhydride, and is derived 
directly from dilactic acid. 

Dilactic acid. Lactide. 

Lactide has been represented by the more simple formula 
Q3jj4Q2^ but its vapor density as well as the depression it 
produces in the freezing points of its solvents show that 
the double formula represents the true constitution of this 
body. 

Lactide occurs in colorless crystals, soluble in water and 
alcohol. It possesses the property of combining directly with 
the elements of water, lactic acid being re-formed ; it also 
combines with ammonia, forming lactamide. 

Paralactic Acid. — This is the lactic acid which may be 
extracted from meat. It is also called sarcolactic acid. It may 
be prepared from commercial extract of meat ; this is dissolved 
in 4 parts of water, and the solution precipitated by 8 parts 
of 90 per cent, alcohol. The alcoholic solution is decanted, 
and the residue, which is insoluble in alcohol, is exhausted with 
2 parts of lukewarm water, the solution again being precip- 
itated by alcohol. The alcoholic solutions are united and dis- 
tilled on a water-bath. The residue is rendered strongly acid 
by sulphuric acid, and agitated with ether which dissolves the 



600 ELEMENTS OF MODERN CHEMISTRY. 

paralactic acid set free. The ethereal solution is evaporated, 
and the acid is converted into the salt of zinc, which is subse- 
quently decomposed by hydrogen sulphide, as has been indicated 
for the preparation of ordinary lactic acid. Paralactic acid is 
syrupy like its isomeride. It turns the plane of polarized light 
to the right (Wislicenus). When heated, it becomes dehy- 
drated, yielding lactide. 

Levolactic Acid. — An acid which rotates the plane of 
polarization to the left, but otherwise identical with para- 
lactic acid, has been obtained by a peculiar fermentation of 
sugar (Schardinger). 

Ordinary lactic acid can be resolved into the two active 
modifications. 

Lactates and Paralactates. — Lactic acid is a monobasic 
acid ; the neutral lactates contain R'C^H50•^ or W'{C'WOy. 
The most characteristic is zinc lactate, Zn(C^H^O^)'^ -f- 3H^0, 
which is but slightly soluble in cold water, and separates from 
its boiling solution in brilliant needles or laminae. 

Zinc paralactate crystallizes with two molecules of water, 
and is much more soluble than the ordinary lactate. 

Calcium lactate, Ca(C^H^O'^)^ -|- 5H^0, crystallizes in 
rounded masses, formed of little needles grouped around a 
common centre. Like all the lactates, it is very soluble in 
water and alcohol. 

Ferrous lactate, Fe(C^H^O^)^ prepared by double decompo- 
sition of calcium lactate and ferrous sulphate, forms greenish, 
crystalline crusts, soluble in water. It is employed in medicine. 

Lactamide, C^H'^NOl — When an alcoholic solution of lac- 
tide is treated with ammonia and the liquid is evaporated, 
crystals are obtained which are soluble in water and alcohol. 
They constitute lactamide. 

C^H«0* + 2NW = 2C^H^N0^ 

Potassium hydrate decomposes lactamide into lactic acid and 
ammonia. 

Lactamide represents ammonium lactate less the elements 
of water. 

cm cm 

CH.OH — H20 = CH.OH 

C0.0(NH4) C0.NH2 

Ammonium lactate. Lactamide. 



HYDRACRYLIC ACID. 601 

HYDRACRYLIC ACID. 

(ethylenelactic, or /J-hydroxypropionic acid.) 

C3H603 = CH2(OH)-CH2-CO.OH 

This acid is formed by the oxidation of normal propjlglycol. 
It is also formed by the action of water and silver oxide on 
^-J-iodopropionic acid. 

CH2I-CH2-C02H 4- AgOH* = CH2.0H-CH''^-C0.0H -f Agl 

/3-Iodopropionic acid. Hydracrylic acid. 

The silver salt formed in the latter reaction is converted into 
the zinc salt, and the latter is decomposed by hydrogen sul- 
phide. 

Hydracrylic acid is syrupy. When heated, it breaks up 
into acrylic acid and water. 

Q3g603 ^ Q3H402 _(_ H^O 

When heated with hydriodic acid, it is again converted into 
/9~iodopropionic acid. Its sodium salt, NaC^H^O^ deposits from 
alcohol in crystals fusible at 142-143°. Between 180 and 200°, 
it loses water, and is partly converted into sodium acrylate. 

Zinc hydracrylate, Zn(C^H^O^)^ + 4H^0, is characteristic. 
It forms large, very brilliant crystals, soluble in about one 
part of water. 

GLYCERIC (DIHYDROXYPROPIONIC) ACID. 

C3H601 = CH2(0H)-CH(0H)— CO.OH 

This acid is obtained by oxidizing glycerol with nitric acid, 
or by treating it with bromine and water. It is also formed 
by the spontaneous decomposition of nitroglycerin. 

It is prepared by introducing into a tall jar one part of nitric 
acid of specific gravity 1.5, and 1 part of glycerol diluted with 
its own volume of water. Care is taken that the two liquids may 
not mix, and the whole is left to itself for five or six days. The 
two bodies gradually mingle and react upon each other. The 
liquid is evaporated on a water-bath, and the residue is boiled 
with well-washed hydrate of lead suspended in water, after 
which the solution of lead-salt is filtered hot. Crystals of lead 

^ Instead of Ag20 + H20. 
2a 51 



602 ELEMENTS OF MODERN CHEMISTRY. 

glycerate separate on cooling; they are purified, and their 
aqueous solution when decomposed by hydrogen sulphide, fur- 
nishes glyceric acid. 

Properties. — Grlyceric acid is a thick, light-yellow syrup, 
soluble in water and alcohol. Its reaction is acid ; it is mono- 
basic. Hydriodic acid, by the aid of heat, converts it into 
/S-iodopropionic acid. Its relations with glycerol may be seen 
in the following formulas: 

CH2.0H CO.OH 

CH.OH CH.OH 

CH2.0H CH2.0H 

Glycerol. Glyceric acid. 



Closely related to glycollic and lactic acids are two important 
nitrogenized bodies, glycocoU and alanine. They form part of 
a series which includes among other bodies leucine, a nitro- 
genized compound which plays a part in the animal economy. 
When a current of nitrous anhydride is passed into solutions 
of glycocoll, alanine, and leucine, nitrogen is disengaged, and 
these bodies are converted into glycollic, lactic, and leucic acids. 
We then have the following series : 

C2H4Q3 C^H^NO^ 

Glycollic acid. Glycocoll. 

C3H6Q3 C^H^NO^ 

Lactic acid. Alanine. 

06^120* C^^H^^NO^ 

Leucic acid. Leucine. 

GLYCOCOLL, OE GLYCINE. 
C2H5N02 = CH2(NH2)-CO.OH 

This body is related to glycollic acid. It was discovered by 
Braconnot, who obtained it by boiling gelatin with dilute sul- 
phuric acid for a long time, saturating the solution with barium 
carbonate and evaporating the filtered liquid. Hence the name 
sugar of gelatin or glycocoll. 

Cahours obtained it by the action of ammonia on mono- 
chloracetic acid. 

?-0H + 2NH3 = NH^C. + f°-0« 
CH2C1 CH2.NH2 

Monochloracetic acid. Glycocoll. 

It is therefore amidacetic acid. 



GLYCOCOLL. 603 

It may also be formed by passing cyanogen gas into boiling 
hydriodic acid, which is reduced with separation of iodine, the 
hydrogen effecting the change. 

Z ^ -- - - = 6™ - - 

It is a solid body, crystallizing in oblique rhombic prisms, 
fusible at 235°. Its taste is sweet. It is soluble in 4 parts of 
water, slightly soluble in alcohol, insoluble in ether. Its solu- 
tion has a feeble acid reaction. Indeed, glycocoll can react with 
the bases, forming compounds ; when it is digested for several 
hours at a temperature between 80 and 104° with silver oxide, 
the latter is dissolved, and the compound C^H^AgNO^ is formed. 
The cupric compound, (C'H^^^O'O'Cu -f H'^0, crystallizes in 
beautiful, dark-blue needles. On the other hand, glycocoll will 
combine with the acids ; there is a nitrate of glycocoll crystal- 
lizable in large prisms containing C^H^NOIHNO^. 

With ferric chloride, glycocoll gives an intense red color de- 
colorized by acids and reappearing on the addition of ammonia. 

When nitrous anhydride is passed into a solution of glycocoll, 
the latter is converted into gly collie acid, nitrogen being at the 
same time disengaged. 

Glycocoll. Glycollic acid. 

MethylglycocoU or Sarcosine, C^H^NO^ — This compound 
is obtained by the reaction of methylamine and monochloracetic 
acid, by an interchange analogous to that which yields glycocoll. 

T^f? + 2NH2(CH3) = NH2(CH3)HC1 + ?^-^^ 

CH2C1 ^ ^ \ ) -r CH2.NH(CH3) 

Monochloracetic Methylamine. Methylamine Sarcosine. 

acid. hydrochloride. 

It is also formed in the decomposition of creatine and caffeine 

by baryta water (Liebig). It crystallizes in rhomboidal prisms, 

very soluble in water, slightly soluble in alcohol. It melts 

and decomposes at 210°-220°, yielding dimethylamine and 

carbon dioxide. Like glycocoll, it forms compounds with 

acids. When distilled with soda-lime, it yields methylamine. 

It may be distinguished from glycocoll by the action of nitrous 

acid, which converts it and all compounds which contain the 

group NH into nitroso-derivatives. 

CO.OH ^„ ^_ CO.OH 

I + OH. NO = I -I-H20 

CH2.NH(CH3) ^ CH2.N(N0)(CH3) ^ "^ 

Sarcosine. Nitrous acid. Nitrososarcosine. 



604 ELEMENTS OP MODERN CHEMISTRY. 

ALANINE. 

C3H7N02 = CH3-CH(NH2)-CO.OH 

Strecker made the synthesis of alanine by passing hydro- 
chloric acid gas into a mixture of aldehyde-ammonia and hydro- 
cyanic acid. 

Cm'O 4- CNH + IFO = C^H^NO^ 

The brown liquid resulting from this reaction is evaporated. 
Alanine crystallizes in hard needles, grouped in stars or tufts. 
It is soluble in water, only slightly soluble in alcohol, insoluble 
in ether. The aqueous solution is neutral, and is converted 
by nitrous anhydride into lactic acid, with evolution of nitrogen. 

2C^H^N0' + N^O^ = 2C^H60^ + H^O + 2N^ 

Alanine. Lactic acid. 

Alanine may be sublimed by cautiously heating it. By dry 
distillation, it breaks up into carbon dioxide and ethylamine. 

C^H^NO^ = CO' + C'HINH^ 

It is isomeric with lactamide and with an acid amide which 

is obtained by the action of ammonia on /9-iodopropionic acid. 

The following formulae account for these isomerides : 

GIF CH2.NH2 CH3 

CH.OH CH2 CH.NH2 

C0.NH2 CO.OH CO.OH 

Lactamide. j8-amidopropionic acid. Alanine. 

^-amidopropionic acid^ which is formed in the reaction just 
indicated, crystallizes in transparent and colorless oblique 
rhombic prisms. It is very soluble in water and but slightly 
soluble in alcohol. It melts at 196°, partly subliming in 
needles, and partly decomposing into ammonia and acrylic acid. 

LEUCINE. 

C6H13N02 

This body was discovered by Proust, in 1818, in old cheese. 
It seems to be identical with a substance obtained from cadav- 
eric fat, and named by Fourcroy aposepedine. It is a product 
of the putrefaction of animal matters. It is also formed when 
horn, gelatinous tissues, or albuminous matters are boiled 
with dilute sulphuric acid, or fused with caustic alkalies. In 



OXALfC ACID. 605 

these reactions, tyrosine, and sometimes glycocoll, is formed 
at the same time. 

Leucine exists already formed in the economy. It is met 
with in the tissues of the liver, spleen, lungs, pancreas, 
salivary glands, etc., and may be formed artificially, by a pro- 
cess analogous to that described for the synthesis of alanine. 

Properties. — Leucine crystallizes in white plates. It dis- 
solves in 27 parts of cold water and much more abundantly 
in boiling water. It melts at 270°, and decomposes at a 
higher temperature into carbon dioxide and amylamine. 

DIAZO-ACIDS. 

A series of interesting and important acids has recently 
been discovered by Curtius as products of the action of po- 
tassium nitrite on hydrochloric acid solutions of the amido- 
acid ethers. While it has not been possible to isolate the 
free acids on account of their tendency to decompose with 
liberation of nitrogen, their ethers are formed quite readily. 
Thus, the action of potassium nitrite on ethyl amido-acetate 
in presence of hydrochloric acid yields ethi/l diazoacetate. 

KN02 + HCl + NH'^CIP-CO.OC2H5= KCl + n >CH-CO.OC2H5 + 2H20 

N 

This ether is a lemon-yellow oil, which may be distilled in 
vacuum, but is decomposed with explosive violence when 
heated under ordinary pressures or on contact with sulphuric 
acid. Nascent hydrogen converts the diazoethers into hy- 
drazine derivatives. Diamide and hydrazoic acid (page 160) 
were first obtained with the aid of these ethers. 

OXALIC ACID. 

C2H204 = CO(OH)-CO(OH) 

Natural State and Modes of Formation. — This important 
acid exists in many vegetables. Wiegleb and Scheele extracted 
it from salt of sorrel, which is an acid oxalate of potassium. 

The process of Scheele has become classic. It consists in 
precipitating a solution of salt of sorrel with acetate of lead, 
and decomposing the precipitated lead oxalate by hydrogen 
sulphide. The great Swedish chemist demonstrated the iden- 

51* 



606 ELEMENTS OF MOf>ERN CHEMISTRY. 

tity of the acid tlius formed and that which Bergman had 
previously obtained by treating sugar with nitric acid. 

Oxalic acid is met with in the animal economy. Urine often 
deposits little crystals of calcium oxalate, which salt is some- 
times deposited in the bladder and there forms rough concre- 
tions known as mulberry calculi. 

Oxalic acid is formed by the action of nitric acid or fused 
caustic potash on a great number of organic matters. 

Cyanogen yields oxalic acid by its decomposition in contact 
with water (page 464). 

We have already studied the relations which exist between 
oxalic acid and glycol (page 579). 

Drechsel has made a synthesis of oxalic acid by passing 
carbon dioxide over metallic sodium disseminated in very 
dry sand and heated to 350°. The product was sodium 
oxalate. 

2C0^ + Na^ =: Na^C^O* 

Sodium oxalate. 

An oxalate also results when sodium or potassium formate 
is rapidly heated to 440°. 

2NaCH0^ = P°-°f + H^O 
CO.ONa 

Preparation. — Oxalic acid is prepared in the arts by two 
processes. One consists in the oxidation of molasses of an 
inferior quality by nitric acid. The operation gives rise to an 
abundant disengagement of nitrous vapors and carbon dioxide. 
It is conducted in leaden boilers that are not attacked in pres- 
ence of a great excess of oxidizable organic matter. 

Another process consists in the reaction of potassium hy- 
drate on saw-dust at a high temperature. The mass is ex- 
hausted with water which dissolves out potassium oxalate, and 
the solution is treated with milk of lime. Calcium oxalate is 
precipitated and potassium hydrate regenerated. The precip- 
itated calcium oxalate is decomposed by sulphuric acid, calcium 
sulphate, which is almost insoluble, being formed, and oxalic 
acid remaining in solution in the water. When the latter is 
sufficiently concentrated, the acid is deposited in crystals. The 
potassium hydrate which remains in the first solution is evapo- 
rated, and serves for new operations. 

Properties. — Oxalic acid crystallizes from its aqueous solu- 
tion in large, transparent prisms, containing 2 molecules of 
water. When exposed to the air, these crystals effloresce, and 



OXAMC ACID. 607 

they completely lose their water at 100° or in a vacuum over 
sulphuric acid. One part of oxalic acid dissolves in 15.5 
parts of water at 10°. It is also very soluble in alcohol. 

It melts in its water of crystallization at 98°, begins to dis- 
engage gases at 132°, and between 155 and 160° breaks up 
into water, carbon monoxide, carbon dioxide, and formic acid. 

C'H^O* == CO^ + CO + WO 

At the same time, a portion of the dry acid escapes decompo- 
sition and sublimes. 

When oxalic acid is heated with sulphuric acid, it is de- 
composed into carbon monoxide, carbon dioxide, and water, 
according to the equation given above. 

Certain chlorides are reduced by ebullition with a solution 
of oxalic acid : hydrochloric acid is formed, and carbon dioxide 
disengaged. Under such circumstances, auric chloride deposits 
metallic gold ; mercuric chloride is reduced to mercurous chlo- 
ride. 

Oxalic acid is a violent poison. In doses of 8, 12, to 20 
grammes, it produces poisonous effects which may prove fatal. 
It acts upon the heart, retarding its movements, and upon the 
nerve centres, of which it rapidly depresses the functions. Its 
antidote is chalk or precipitated calcium carbonate. 

If a solution of oxalic acid, or better, ammonium oxalate, 
be added to a solution of calcium chloride, a white precipitate 
of calcium oxalate is formed. This precipitate is formed even 
in very dilute solutions, and is insoluble in acetic acid. 

If a small quantity of silver oxalate be heated in a small 
test-tube, the salt decomposes with explosive violence into 
carbon dioxide and metallic silver : a portion of the latter is 
projected from the tube, while the remainder is left as a 
gray powder. 

These reactions characterize oxalic acid. 

Oxalates. — Oxalic acid is dibasic. Its two atoms of hydro- 
gen may be replaced by two atoms of a univalent metal, or by 
one atom of a bivalent. Acid oxalates and neutral oxalates 
are known. 

Potassium Acid Oxalate, KHC^O* -{- H^O.— This salt con« 
stitutes the greater part of the salt of sorrel of commerce. It 
is extracted from the juice of various kinds of Rumex and 
Oxalis^ the juice of which is clarified with clay and then evap- 
orated to crystallization. It is but slightly soluble in water. 



608 ELEMENTS OF MODERN CHEMISTRY. 

If a concentrated solution of oxalic acid be agitated with a 
solution of potassium neutral oxalate, a precipitate of potassium 
acid oxalate will be formed. 

If a concentrated solution of oxalic acid be agitated with 
a solution of potassium acid oxalate, a white precipitate of 
potassium quadroxalate, a combination of the acid salt and 
oxalic acid, will be deposited. It contains C^ffO* -j- KHC^O* 
+ 2W0. 

Neutral Potassium Oxalate, K^C^O* -|- H^O, is obtained 
by neutralizing a solution of the acid salt with potassium car- 
bonate and evaporating. It crystallizes in oblique rhombic 
prisms, very soluble in water. 

Ammonium Oxalate, (NH^^C^O* + H^O, which is fre- 
quently used as a reagent, is prepared by neutralizing oxalic 
acid with ammonia. The concentrated solution deposits color- 
less crystals belonging to the type of the right rhombic prism. 
There is also an acid oxalate of ammonium, (NH*)HC^O*. 

Methyl Oxalate, (Cff)^C^O*, forms colorless crystals melt- 
ing at 54°. It is prepared by heating anhydrous oxalic acid 
with methyl alcohol. 

Ethyl Oxalate, or Oxalic Ether, (C='H5)^C=^0^— This ether 
may be prepared by distilling a mixture of potassium acid 
oxalate, alcohol, and concentrated sulphuric acid. It is a 
colorless oily liquid, heavier than water, and having an aro- 
matic odor. It boils at 186°. 

OXAMIDE. 

If solution of ammonia be added to ethyl oxalate, the latter 
immediately solidifies to a white mass formed of a crystalline 
powder. This is oxamide. 

^2^5;q>C202 + 2NH3 = C202<^^2 _^ 2(C2H5.0H) 
Ethyl oxalate. Oxamide. 

Oxamide is also formed by the dry distillation of ammonium 
oxalate. 

NHto>^'^' = C202<^H2 ^ 2H20 

The latter reaction, studied in 1830 by Dumas, led to the 
discovery of the amides. 

Oxamide is a white, crystalline powder, very slightly soluble 



MALONIC ACID. 



609 



in cold water, insoluble in alcohol, somewhat soluble in boiling 
water, from which it is deposited on cooling. Like all of the 
amides, it is decomposed by boiling caustic alkalies, ammonia 
being disengaged and potassium oxalate formed. 

Oxamic Acid. — This body is formed when ammonium acid 
oxalate is heated to between 220 and 238° (Balard). 

Ammonium acid oxalate. Oxamic acid. 

It is a yellowish, granular powder which boiling water con- 
verts into ammonium acid oxalate by the direct addition of 
one molecule of water. 

The following formulae express clearly the relations existing 
between oxalic acid, oxamic acid, and oxamide : 

C^OKoi C202<Oh' C202<^g 

Oxalic acid. Oxamic acid. Oxamide. 



MALONIC ACID. 

C^H^O* = cs'<caoH 
Malonic acid is the next higher homologue of oxalic acid, 
and was first obtained by the oxidation of malic acid by po- 
tassium dichromate and sulphuric acid. It also results from 
the hydration of cyanacetic acid when that compound is 
heated with alkalies or with hydrochloric acid. 
CH'<CO.OH + 2ffO = CH^<CO;OH ^ ^^. 

Cyanacetic acid. Malonic acid. 

It crystallizes in colorless thin plates, readily soluble in water 
and alcohol, and fusible at 132°. At a high temperature it 
decomposes into carbon dioxide and acetic acid. 

It is dibasic, like oxalic acid forming two series of salts in 
which either one or both atoms of basic hydrogen are replaced 
by an equivalent quantity of metal. 

Ethyl Malonate, (G'WyC'WO\ can be prepared by the 
action of hydrochloric acid gas on a mixture of alcohol and 
calcium malonate. It is a colorless liquid, boiling at 198°. 
When heated with water to 150°, it is decomposed into ethyl 
acetate, carbon dioxide, and ethylene. The hydrogen atoms 
in the acid radical of ethyl malonate can be successively 
replaced by sodium, and the reactions of the sodium malonic 



610 ELEMENTS OP MODERN CHEMISTRY. 

ethers so formed render them valuable agents in many syn- 
theses (see Succinic Acid). 

Oxymalonic or Tartronic Acid, C^H*0^ is one of the 
products of the decomposition of tartaric acid by nitric acid, 
page 617. Its formula is 

CO.OH 
CH.OH 
CO.OH 
It forms large colorless prisms, fusible at 184°. 

SUCCINIC ACID. 

C4H604 = CO.OH-CH2-CH2-CO.OH 

This acid, which was first obtained by the distillation of 
amber, is one of the products of oxidation by nitric acid of the 
complex fatty acids, such as palmitic and stearic acids. It is 
also formed in the alcoholic fermentation of sugar (see page 
648), in the fermentation of calcium malate, and by the re- 
duction of malic and tartaric acids by hydriodic acid. 

Maxwell Simpson obtained it synthetically by decomposing 
ethylene dicyanide with potassium hydroxide. 

+ 2NH3 



CH2-CN 




CH2-C0.0H 




4H20 




CH2-CN 




"~ CH2-C0.0H 


lene dicyanide. 




Succinic acid. 



In this reaction the nitrogen of each cyanogen group unites 
with H^ and is replaced by O'H == 2(H20) — H'. Succinic 
acid thus contains two groups CO^H, combined with ethylene. 

When the monosodium compound of malonic ether reacts 
with chloracetic ether the ethyl ether of ethenyltricarboxylic 
acid is formed. 

CHNa=(C00C2H5)2 + CH2C1-COOC2H5 = 
Sodium malonic ether. Chloracetic ether. 
NaCl + COO(C2H6)-CH2-CHrz(COOC2H6)2 
Ethenyltricarboxylic ether. 

By the action of heat the free acid obtained by saponifi- 
cation of the latter ether is decomposed into carbon dioxide 
and succinic acid. All acids containing two carboxyl groups 
combined with the same carbon atom are decomposed with 
loss of carbon dioxide in an analogous manner. 

Preparation. — Succinic acid is manufactured by the dry 
distillation of amber and purifying the solid product of this 
distillation. 



SUCCINIC ACID. 611 

Properties. — Succinic acid forms large, colorless crystals, un- 
altered by the air, and fusible at 180°. At 235° it boils and 
breaks up into succinic anhydride and water. 

Succinic acid. Succinic anhydride. 

It is fairly soluble in water, less so in alcohol, and almost in- 
soluble in ether. 

Succinic anhydride^ C*H*0^, which is formed as above men- 
tioned by the dry distillation of succinic acid, forms a white, 
crystalline mass. It is converted by phosphorus pentachloride 
into succinyl chloride, C^H^O'CP. 

CH2-C0^ , CH2-C0C1 

I >o -I- PC15 = pocp + Y 

CH2-C0^ CH2-C0C1 

Succinic anhydride. Succinyl chloride. 

Kekule has obtained monohromo-succinic and dibromo-suc- 
cinic acids by heating moistened succinic acid with bromine in 
sealed tubes. 

Monobromo-succinic acid is converted into malic acid when 
treated with water and silver oxide. 

C2H3Br<^22§ + AgOH = C2H3(OH)<gg| + AgBr 
Monobromo-succinic acid. Malic acid. 

Under the same circumstances, dibromo-succinic acid is con- 
verted into tartaric acid. 

C2H2Br2<gg2H + 2AgOH = C2H2(OH)2<^g2n + ^AgBr 
Dibromo-succinic acid. Tartaric acid. 

These reactions, which were discovered by Kekule, establish 
very close relations between succinic, malic, and tartaric acids. 

CH2-C0.0H 

I succinic acid. 

CH2-C0.0H 

CH(OH)-CO.OH 
I malic acid. 

CH2-C0.0H 

CH(OH)-CO.OH 
1 tartaric acid. 

CH(OH)-CO.OH 

Malic acid is oxysuccinic acid, and tartaric acid is dioxysuc- 
cinic acid. By reducing agents, the latter acids can be con- 
verted into succinic acid. When either of them is heated with 
a large excess of hydriodic acid, water is formed, iodine is de- 



612 ELEMENTS OF MODERN CHEMISTRY. 

posited, and the liquid will be found to contain succinic acid 
(Schmitt and Dessaignes). 

CO OH 
Isosuccinic Acid, ^H^~^^<no oH' ^^°"^^^^^ ^^^^ ^^°" 

cinic acid, is obtained by boiling with potassium hydrate the 
cyanide of ethylidene^ CH^-CH(CN)^, corresponding to the 
chloride CH^-CHCP. It crystallizes in needles, fusible at 130°, 
and more soluble in water than succinic acid. 

MALIC ACID. 
C*H605 = C0.0H-CH2-CH(0H)-C0.0H 

This acid, which exists in a number of vegetables, was ex- 
tracted by Scheele from apple-juice. It is generally prepared 
from the berries of the mountain-ash, gathered before their 
complete maturity ; they are strongly pressed, and the juice is 
boiled, filtered, and neutralized with milk of lime at the ordi- 
nary temperature. Calcium malate is deposited, and this is 
converted into the acid malate by dissolving it in boiling water 
acidulated with nitric acid. The calcium acid malate may be 
readily purified by crystallization, after which it is converted 
into malate of lead by double decomposition with lead acetate. 
The lead salt is suspended in pure water and decomposed by 
hydrogen sulphide ; the filtered solution is then evaporated. 
Properties. — Malic acid crystallizes in little needles grouped 
in rounded grains. These deliquesce when exposed to the air. 

This acid presents three isomerides. Their solutions have 
a sour taste ; one of them, the natural acid, rotates the plane 
of polarized light to the left, another to the right, and the 
third is optically inactive. They are identical in structure, 
and must be regarded as stereoisomeric (see page 614). 
Malic acid solutions 3o not produce a cloud in lime-water, 
neither in the cold, nor on boiling. 

When malic acid is heated, it begins to lose water at 130°, 
and between 150 and 200° is converted into two acids which 
are isomeric with each other, and are known as maleic and 
fumaric acids. 

Q4JJ605 ^ C^H^O* + H^O 

Malic acid. Maleic and fumaric acids. 

Fumaric acid forms colorless prisms, not very soluble in cold 
water, and not fusible but volatilizing with partial decomposi- 



ASPARAGIN AND ASPARTIC ACID. 613 

tion above 200°. Nascent hydrogen converts it into succinic 
acid. 

Maleic acid resembles fiimaric acid, but is mucb more soluble 
in water. It melts at 130°^ and at 160° decomposes into maleic 
anhydride and water. The differences in the constitution of 
these two acids are not clearly understood. Both are prob- 
ably represented by the formula CO.OH-CH-CH-CO.OH ; 
they may be stereoisomeric. 

By the action of potassium hydrate at about 150°, malic 
acid is decomposed into oxalic and acetic acids. 

C^H^O^ _|_ H^o =: (TWO' + C^H^O^ + W 

Malic acid. Oxalic acid. Acetic acid. 

ASPARAaiN AND ASPABTIC ACID. 

Succinic and malic acids present simple and remarkable rela- 
tions with two nitrogenized bodies which have long been known ; 
they are asparagin and aspartic acids. 

The latter body is amidosuccinic acid, and bears the same 
relations to succinic acid that glycocoll (amido-acetic acid) 
bears to acetic acid. On the other hand, its relations to malic 
acid are analogous to those of glycocoll to glycollic acid. 
CH3 CIP.OH CH2.NH2 

CO.OH CO.OH CO.OH 

Acetic acid. Glycollic acid. Glycocoll. 

CH2-C0.0H CH2(0H)-C0.0H CH(NH2)-C0.0H 

CH2-C0.0H CH2-C0.0H CH^-CO.OH 

Succinic acid. Malic acid. Aspartic or amidosuccinic acid. 

Asparagin is the monamide of aspartic or amidosuccinic acid ; 
it is isomeric with the diamide of malic acid. 

CH(NH2)-CO.NH2 CH.0H-C0.NH2 

CH2-C0.0H CH2-CO.NH2 

Asparagin. Malamide. 

Asparagin, C^H^N^Ol — This body exists naturally in aspa- 
ragus, black salsify, the roots of marsh-mallow, licorice wood, 
and in the buds of cereals, peas, vetches, and beans before they 
flower. To extract it from these vegetables, they are expressed 
while fresh, and the juice is clarified and concentrated. The 
asparagin is deposited in colorless crystals. It is only slightly 
soluble in cold water and alcohol, but is more soluble in hot 
water. It forms combinations with both bases and acids. 

52 



614 ELEMENTS OF MODERN CHEMISTRY. 

When boiled witli tliese agents, it loses ammonia and is con- 
verted into aspartic acid. 

Asparagin. Aspartic acid. 

Aspartic Acid, C^H^NO*, forms rhombic crystals, slightly 
soluble in cold, and more soluble in hot water. Like gly- 
cocoll, aspartic acid can form compounds with both acids 
and bases. 

TARTARIC ACID, OR DIOXYSUCCINIC ACID. 

C4H606 = CO.OH-CH(OH)-CH(OH)-OO.OH 

This acid exists in four distinct modifications, — namely, 
dextrotartaric acid, levotartaric acid, mesotartaric acid, and 
racemic acid. They all have the same molecular structure : 
they are symmetrical dioxyderivatives of succinic acid, and 
must be regarded as stereoisomer ic. 

This kind of isomerism, which has been mentioned before, 
is believed to be due to differences in the spatial arrangement 
of the atoms within the molecules. It cannot be expressed 
by the ordinary structural formulas. Van't Hofi" has shown 
that optical activity (power to rotate the plane of polariza- 
tion) is confined to substances containing one or more carbon 
atoms of which the four atomicities are satisfied by four dis- 
tinctly different atoms or radicals. Such carbon atoms he 
designates as asymmetric. He conceives the carbon atom 
placed in the centre of a tetrahedron, and the four atoms or 
radicals combined with it at the angles of the tetrahedron. 
Two different arrangements of the different groups with 
reference to the carbon atom are possible, and the resulting 
configurations are to each other as an object is to its mirror- 
image : they are enantiomorphous. They would have opposite 
rotatory power, but their chemical properties would be identical. 

Lactic and malic acids, for example, both contain an asym- 
metric carbon atom, and both exist in three modifications dif- 
fering in their behavior toward polarized light and in other 
physical properties. 

The molecule of tartaric acid contains two such asym- 
metric carbon atoms, directly united, and each of these is 
combined with a hydrogen atom, a hydroxyl group, and 
a carbonyl group. Three configurations are possible, — a 



TARTARIC ACID, OR DIOXYSUCCINIC ACID. 



615 



dextro-form, in which both asymmetric carbon atoms are 
positive, a levo-form, in which both are negative, and an in- 
active variety, in which one is positive and the other negative. 




COOH 

a. Dextrotartaric acid. 




OH 
CdOH 

b, Levotartaric acid. 



COOH 

c, Mesotartaric acid. 



a and b are optically active : each contains two similar asymmetric 
carbon atoms ; c is inactive because the two asymmetric atoms neu- 
tralize each other (internal compensation). 

There is possible still another inactive modification formed 
by the union of equal molecular proportions of the two active 
varieties (^external compensation). This is racemic acid ; it is 
capable of being split up into dextro- and levo-tartaric acids. 

Dioxysuccinic acid has been obtained synthetically in sev- 
eral ways. By heating succinic acid with bromine and water, 
dibromosuccinic acid is obtained ; when this is boiled with 
water and silver oxide, it is converted into the dioxyderiva- 
tive, thus : 



CHBr-COOH 
CHBr-COOH 



+ 2AgOH 



CH(OH)-COOH 
CH(OH)-COOH 



+ 2AgBr 



The synthesis of racemic acid was effected by Strecker; 
he converted glyoxal into the corresponding dicyanohydrin, 
which he then decomposed by hydrochloric acid. 



„„^,, CH OH-CN 

-h 2HCN =1 

CH(OH)-CN 



CHO 

CHO 

CH(OH)-CN CH(OH)-COOH 

' ' + 4H30 =1 



CH(OH)-CN 



CH(OH)-COOH 



+ 2NH8 



616 



ELEMENTS OF MODERN CHEMISTRY. 



DEXTROTARTARIC ACID (ORDINARY TAR- 
TARIC ACID). 

This is one of the most widely distributed of the vegetable 
acids. It was discovered by Scheele in the tartar, or argol, 
which is deposited in casks in which wine is kept. It is 
prepared from purified tartar, called cream of tartar, which 
is acid tartrate of potassium. 

Preparation. — The salt is dissolved in boiling water, and 
chalk is added until all effervescence, due to the disengage- 
ment of carbon dioxide, ceases. Insoluble calcium tartrate is 
deposited, and potassium neutral tartrate remains in solution. 
The calcium tartrate is collected on a filter, and the filtrate is 
precipitated by calcium chloride. A new portion of insoluble 
calcium tartrate is thus obtained, and is washed and united with 
the first portion. This salt is then suspended in water and 
exactly decomposed by dilute sulphuric acid ; calcium sulphate 
is precipitated, and separated by filtration, and the filtered 
liquid, when sufficiently concentrated and allowed to evaporate 
in a warm place, deposits crystals of tartaric acid. 

Properties. — Tartaric acid crystallizes in large, oblique rhom- 
bic prisms, which often present hemihedral facettes. They are 
unaltered by the air, and dissolve in about half their weight 
of cold water and still more abundantly in boiling water. 
They dissolve also in alcohol, but not in ether. 

The aqueous solution of tartaric acid turns the plane of 
polarization to the right. It forms white precipitates in lime- 
water and baryta-water, but an excess of the acid redissolves 
these precipitates. 

If an excess of tartaric acid be added to a solution of cupric 
sulphate, the liquid may be saturated with caustic potash, but 
no precipitation of cupric hydroxide will take place. The 
liquid will remain transparent and will assume a beautiful 
dark-blue color; it is known as FcliUng^s solution. In the 
same manner, ferric chloride, to which tartaric acid has been 
added, is not precipitated by alkaline hydroxides. 

When tartaric acid is fused with caustic potash, it is de- 
composed into acetic and oxalic acids. 

Action of Heat on Tartaric Acid. — 1. Tartaric acid fuses 
between 167 and 170°, and when the action of the heat is 
not prolonged, it is converted into isomeric mesotartaric acid. 



TARTRATES. 617 

Prolonged heating to 165° in sealed tubes, of tartaric acid 
with a small quantity of water, transforms it into mesotar- 
taric and racemic acids. 

2. If the acid be maintained for some time in fusion, it 
loses water and is converted into clitartaric acid. 

Ditartaric acid. 

3. When 15 or 20 grammes of tartaric acid are suddenly 
heated over a naked flame for four or five minutes, the mass 
swells up and a deliquescent, yellow, spongy mass is obtained, 
which constitutes what is called tartaric anhydride. 

Q4JJ6Q6 ^ C*H*05 + H^O 

Tartaric anhydride. 

When heated for some time to 150° in a hot-air oven, tar- 
taric anhydride becomes insoluble. 

4. When tartaric acid is distilled by heating it gradually in 
a retort to 300°, it yields besides other products two pyro- 
genous acids, pyruvic and pyrotartaric acids. 

Pyruvic acid. 

2C*HW = C^H«0* + 3C0^ + 2H^0 

Pyrotartaric acid. 

Action of Nitric Acid upon Tartaric Acid. — Very con- 
centrated nitric acid converts tartaric acid into nitrotartaric 
acid, C*H*(NO^)^0^ (Dessaignes). This body may be obtained 
in crystals, but it is not stable. Its aqueous solution decom- 
poses between 40 and 50°, with a brisk effervescence of carbon 
dioxide, and formation of oxalic acid. When the decompo- 
sition takes place below 36°, a peculiar, crystallizable acid is 
formed, which Dessaignes has named tartronic acid. Its com- 
position corresponds to the formula C^H*0^ (see page 610). 



TARTKATES. 

Tartaric acid is dibasic ; it contains two hydrogen atoms 
which are replaceable by an equivalent quantity of metal. 
Neutral tartrates and acid tartrates are known. 

H I C4H406 jH I c4H*06 Jj; I C4H*06, or R"C*HiO« 

Tartaric acid. Acid tartrates. Neutral tartrates. 

52* 



618 



ELEMENTS OF MODERN CHEMISTRY. 



Neutral tartrates are known in which one atom of metal 
is replaced by a monatomic oxidized group, such as (SbO)', 
(FeOy, (BOy. 
K 



C4H406 



C4H406 



Potassium Tartar-emetic, 

acid tartrate. 



K 

(FeO)' 
Ferro-potassium tartrate. 



C4H*06 



C*H*06 



K 

(BO)' 
Boro-potassium 
tartrate. 



Potassium Acid Tartrate, or Cream of Tartar, KHC*H*0^ 

is prepared from the crude tartar of wine-casks by subjecting 
that product to several crystallizations in boiling water. It 
crystallizes in right rhombic prisms, very slightly soluble in 
water. If a concentrated solution of tartaric acid be added 
to a saturated solution of potassium chloride, a precipitate of 
potassium acid-tartrate will be formed on agitating the 
liquid. This reaction serves as a characteristic test for tar- 
taric acid. 

Potassium Neutral Tartrate, K'C*II*0^— This salt is pre- 
pared by neutralizing a boiling solution of cream of tartar 
with potassium carbonate. The evaporated solution deposits 
on cooling oblique rhombic prisms, very soluble in water. 

Potassium and Sodium Tartrate, j^^j c^H^oe + 4H20.-This 
salt, which is much used in medicine, was discovered in 1672 
by Seignette, a pharmacist of Rochelle ; hence it is often called 
Rochelle salt, or Seignette's salt. It is prepared by neutralizing 
a boiling solution of cream of tartar with sodium carbonate, and 
evaporating the solution. On cooling, the double tartrate is 
deposited in large, beautiful crystals, eight-sided right rhombic 
prisms. 



POTASSIUM ANTIMONYL TARTRATE, 
TARTAR EMETIC. 



OR 



(Sboy I 



C^iQe 



This salt is prepared by boiling cream of tartar with water 
and oxide of antimony, which dissolves abundantly in the 
liquid. After filtration and cooling, the salt is deposited in 
crystals which are purified by a second crystallization. 

Tartar-emetic crystallizes in rhombic octahedra, and the crys- 
tals, which contain one molecule of water of crystallization for 
two molecules of salt, effloresce in dry air. 

Its taste is astringent and nauseating. It dissolves in 14.5 



BACEMIC ACID. 619 

parts of cold water and in about two parts of boiling water. 
It is insoluble in alcohol. 

When heated to 200° it loses the elements of water and is 
converted into a double tartrate of antimony and potassium, in 
which the trivalent antimony replaces 3 atoms of hydrogen in 
the tartaric acid. 

C*H*(SbO)'KO« = eH^Sb'^HKO^ + H^O 

When heated to redness in a small, covered crucible, tartar- 
emetic leaves an alloy of potassium and antimony, disseminated 
in a mass of charcoal. When this mass is exposed to moist 
air, it suddenly takes fire and explodes, projecting brilliant 
sparks. 

The following are the characteristics of a solution of tartar- 
emetic : 

Hydrogen sulphide forms an orange precipitate of antimony 
sulphide. 

A few drops of hydrochloric acid cause the appearance of 
a white precipitate of antimony oxychloride, which disappears 
in an excess of acid. 

Potassium hydroxide produces a white precipitate of anti- 
mony oxide, which redissolves in an excess of alkali. 

A plate of tin immersed in a solution of emetic precipitates 
metallic antimony as a black deposit. 

Tartar-emetic is a much employed medicine. In large doses, 
or smaller ones frequently repeated, it is an energetic poison. 
It is also used as a mordant in calico-printing. 

Ferro-Potassium Tartrate. — This salt is prepared by dis- 
solving ferric hydrate in cream of tartar, and evaporating the 
solution. It forms brown, amorphous scales, very soluble in 
water. It is used in medicine. 

Boro-potassium Tartrate is formed when boric acid is dis- 
solved in a boiling solution of cream of tartar. It is an amor- 
phous salt, very soluble in water. 

RACEMIC ACID (PARATARTARIC ACID). 

C8H12012 + 2H20 

This acid was discovered in 1822 by Kestner, and has been 
studied by Berzelius and by Pasteur. 

It crystallizes in transparent, triclinic prisms, which efflo- 
resce in the air, losing their water of crystallization. It dis- 



620 ELEMENTS OF MODERN CHEMISTRY. 

solves in 5.7 parts of water at 15°. Its solution does not 
change the plane of polarized light, but Pasteur has succeeded 
in separating it into two other acids, both of which are optically 
active. One of them turns the plane of polarization to the 
right, and is ordinary tartaric acid ; the other deflects it to the 
left, and is levo-tartaric acid. These two acids, which are iso- 
meric with each other, reproduce racemic acid when they 
are mixed in equivalent proportions. It is somewhat remark- 
able that the mixture of their solutions is attended by a 
development of heat (Pasteur). 

The solution of racemic acid precipitates solutions of sul- 
phate, nitrate, and chloride of calcium, a character which 
tartaric acid does not possess. 

Mesotartaric Acid, or inactive tartaric acid, has no action 
on polarized light, but cannot be split up into the active varie- 
ties. It is also more soluble than racemic acid, and its salts 
are well characterized. 

PYROGENOUS ACIDS DERIVED FROM TAR- 
TARIC ACID. 

Pyruvic Acid, C^HW = Cff-CO-CO.OH.— This acid, 
which is produced by the dry distillation of glycerol, tartaric 
and pyrotartaric acids, is formed synthetically by the action of 
concentrated hydrochloric acid on acetyl cyanide. 

. CO.CN + 2H^^ = ^^<?00H + ^S^ 

Acetyl cyanide. Pyruvic acid. 

This reaction determines the constitution of pyruvic acid, and 
shows that it contains the group carbonyl, CO, like acetone, 
CH^-CO-CH'\ All acids containing the group CO are called 
ketonic acids. 

Pyruvic acid is a liquid, soluble in water, alcohol, and ether ; 
its odor is like that of acetic acid. It boils at 165-170°, being 
partially decomposed into carbon dioxide and pyrotartaric acid. 
2C^H*0^ = CO' -f C^H«0* 

Tyruvic acid. Pyrotartaric acid. 

With sodium acid sulphite it forms a crystallizable compound, 
an evidence of its ketonic nature, as is also its behavior to- 
wards hydroxylamine and phenylhydrazine. With the latter 
it gives a very characteristic hydrazone, CII^C(N^HC^H5) 
COOH. 



CITRIC ACID. 621 

Under the influence of nascent hydrogen it yields ordinary 
lactic acid. 

CH^'-CO-CO.OH + H^ = CH^-CH.OH-CO.OH 

Methyl-succinic, or Pyrotartaric Acid, C^H^O*.CH^-CH 
(CO.OH)-CH^-CO.OH.— This acid, of which the mode of 
formation has been already indicated, is one of the four acids 
of the formula C^H^O*, of which theory predicts the existence, 
and all of which are actually known. It has been obtained 
synthetically by the action of boiling potassium hydroxide on 
propylene cyanide. 

cm CH3 

CH.CN + 4H20 = CH-CO.OH + 2NH3 

CH2CN CH2-C0.0H 

Propylene cyanide. Pyrotartaric acid. 

It is prepared by rapidly distilling a dry mixture of tartaric 
acid and pumice-stone. 

It crystallizes in small prisms, soluble in water, alcohol, and 
ether. It melts at 112°. When heated for a long time to 
about 210°, it decomposes into carbon dioxide and butyric acid. 

Glutaric Acid, ^^^^ch^-CO OH' ^^ formed when tri- 
methylene cyanide, CHICN-CH^-CH^-CN, derived from 
trimethylene chloride, is boiled with potassium hydrate. 

It crystallizes in large clinorhombic tables, fusible at 97°, 
soluble in 1.2 parts of water at 14°. It distils almost unaltered 
towards 300° (Reboul). 

CITRIC ACID. 

C6H807 

This acid, discovered by Scheele in 1784, is widely diffused 
throughout the vegetable kingdom. Itexists in lemons, oranges, 
limes, currants, raspberries, cherries, etc. 

It may be advantageously prepared from lemon-juice, which 
is allowed to stand until it begins to ferment, and is then filtered, 
and saturated with chalk while boiling. The precipitate of 
calcium citrate is washed with boiling water, and decomposed 
by a slight excess of dilute sulphuric acid. The liquid sepa- 
rated from the calcium sulphate yields crystals of citric acid 
after concentration. 



622 



ELEMENTS OF MODERN CHEMISTRY. 



Grimaux and Adam have made tlie synthesis of citric acid 
from dichloracetone, CH^Cl-CO-CH^Cl, which is produced by 
the dehydration of a dichlorhydrin (page 588) by a mixture of 
potassium dichromate and sulphuric acid. Like all of its ana- 
logues, this acetone combines directly with hydrocyanic acid, 
yielding the cyanide 

CH^Cl 

HO-A-CN 

(^ffCl, 

which by the action of alkalies or acids (hydrochloric acid 
answers best) yields the acid 

CH^Cl 
HO-(^-CO.OH 

Ah^ci 

An alcoholic solution of the sodium salt of the latter acid 
(dichloroxisobutyric) heated with potassium cyanide furnishes 
the cyanide 

HO-C-CO.OH 

This is saturated with hydrochloric acid gas, and a solution 
containing citric acid is obtained, from which calcium citrate is 
precipitated when the liquid is neutralized with milk of lime. 

CH^-CN Cff-CO.OH 

HO-C-CO.OH + 4H^0 = HO-(i-CO.OH + 2NH» 

hw-w. Ah^-co.oh 

Properties. — This acid forms large, colorless crystals, derived 
from a right rhombic prism. It dissolves in three-fourths its 
weight of cold and half its weight of boiling water. 

Careful heating with sulphuric acid converts citric acid into 
acetone-dicarhoxylic acid^ carbon monoxide being disengaged. 
CH^-COOH 



C^H«0^ = CO 



+ CO + H^O 



CH^^-COOH 

The solution of citric acid has an acid reaction and a very 
sour taste. It does not precipitate lime-water in the cold, but 
the solution upon heating deposits a crystalline precipitate. 



PYROGENOUS ACIDS DERIVED FROM CITRIC ACID. 623 

Citric acid is tribasic. 

Magnesium citrate, wliicli is soluble, is employed in medi- 
cine ; it is a purgative, having a sweetish taste. Ferric citrate 
also is used in medicine. 

PYROGENOUS ACIDS DERIVED FROM CITRIC 
ACID. 

Aconitic Acid, C^H^O^ — When citric acid is heated, it 
melts; at 176° it disengages water and is converted into 
aconitic acid. 

CH2-C0.0H CH2-C0.0H 

HO-C-CO.OH = C-CO.OH + H20 

Cp2_cO.OH CH-CO.OH 

Citric acid. Aconitic acid. 

Aconitic acid was first obtained from aconite (Aconitum Na- 
pellus). It also exists in shave-grass {Equketum fluviatile) and 
in sugar-cane. It crystallizes in little scales, soluble in water, 
alcohol and ether. It fuses at 191°, and when further heated 
it loses carbon dioxide, and is converted into itaconic acid and 
citra conic anhydride. 

C«H«0« ^ QO^ + C^H^O* 

Itaconic and citraconic acids. 

C^H^O* = C^H^O=^ -f H'O 

Citraconic anhydride. 

Aconitic acid, being unsaturated, is converted by the action 
of sodium amalgam into tricarballylic acid by combining with 
two atoms of hydrogen. 

CH-CO.OH CH2-C0.0H 

C-CO.OH + H2 - CH-CO.OH 

CH2-C0.0H CH2.C0.0H 

Aconitic acid. Tricarballylic acid. 

The latter acid is so named because it was first obtained by 
the hydration of allyl tricyanide, C^H^(CN)^ corresponding to 
allyl tribromide, or tribromhydrin (page 589). 

Itaconic, Citraconic, and Mesaconic Acids, C^H^O*.— 
These three acids are isomeric. The first two are formed by 
the action of heat on citric and aconitic acids ; and they both 
are by dehydration converted into citraconic anhydride. Citra- 
conic acid is converted into mesaconic acid when it is boiled 
with dilute nitric acid, or when heated to 100° with concen- 



624 ELEMENTS OF MODERN CHEMISTRY. * 

trated hydrochloric acid. The three acids are unsaturated, 
and can combine with nascent hydrogen, forming pyrotartaric 
acid. 

Q5JJ604 ^ H^ = C^H«0* 

Itaconic acid crystallizes in rhomboidal octahedra, fusible at 
161°, soluble in seventeen parts of water at 10°. When 
strongly heated it yields citraconic anhydride, which distils. 

Citraconic acid crystallizes in quadratic tables, fusible at 80°. 
It is much more soluble in water than itaconic acid, and deli- 
quesces in moist air. Its anhydride, C^H*0^ is an oily liquid, 
boiling at 213-214°. On contact with water it regenerates 
citraconic acid. 

Mesaconic acid forms brilliant prisms, fusible at 202°, only 
slightly soluble in cold water. At 250° it decomposes into 
water and citraconic anhydride. 

The isomerism of citraconic and mesaconic acids is analo- 
gous to that of maleic and fumaric acids, and is probably a 
case of stereoisomerism. 



URIC ACID. 

^NH— CO-C-NH 
C0< II >C0 

NH C-NH^ 

This body is related to the complex organic acids which 
have just been studied. Among the numerous products do- 

COOH 

rived from its oxidation, we may mention oxalic acid, i , 

^ ' COOH' 

and an acid, CO(COOH0 + H^O or C(0H)XC00H)2, which 
has been called mesoxalic. 

Uric acid was discovered by Scheele, and its numerous meta- 
morphoses were the subject of a classic research by Liebig and 
Wohler, and have been more recently studied by Baeyer and 
other chemists. 

Preparation. — Uric acid may be extracted from the excre- 
ments of serpents, from guano, and from certain urinary cal- 
culi, which are almost entirely composed of it. These sub- 
stances are reduced to a fine powder, boiled with potassium 
carbonate and lime, and the solution filtered. The colored 
solution of potassium urate is mixed with a solution of ammo- 
nium chloride, which produces a white precipitate of ammonium 



URIC ACID. 625 

urate. This salt is well washed, and treated with hydro- 
chloric acid, which sets free uric acid. 

J. Horbaczewski has made the synthesis of uric acid by 
heating a mixture of urea and glycocoU to 200-230°. 

Urea. GlycocoU. Uric acid. 

According to Behrend and Roosen, it is also obtained, and 
in much larger quantity, by heating a mixture of isodialuric 
acid, urea, and sulphuric acid. 

NH-CO-C-OH NH2 NH-CO-C-NH^ 

C0< II +C0< =C0< II >CO + 2H20 

NH C-OH NH2 NH C-NH 

Isodialuric acid. Urea. Uric acid. 

Properties. — Pure uric acid is a light, white powder, which 
has a crystalline aspect under the microscope. When slowly 
separated from dilute solutions, it sometimes forms larger crys- 
tals, containing 2 molecules of water of crystallization. It is 
often deposited from urine in small rhomboidal tables of a 
brownish-yellow color. 

Uric acid is insoluble in alcohol and in ether. It requires 
15,000 parts of cold water, or 1800 parts of boiling water, 
for its solution. It dissolves in solutions of the alkalies, form- 
ing neutral urates containing two atoms of the alkaline metal. 
It is therefore a dibasic acid. When carbonic acid gas is 
passed into a solution of a neutral urate, an acid urate, which 
is almost insoluble, is precipitated. 

Hydrochloric acid forms ^ a thick, white, gelatinous precip- 
itate of uric acid when added to the solution of a urate. 

When uric acid is heated to 160 or 170° with an excess of 
hydriodic acid, it absorbs water, and is decomposed into glyco- 
coU, carbonic acid gas, and ammonia (Strecker). 

C^H^N^O^ -f 5H^0 = C^H^NO^ + 3C0^ -f 3NH' 

Uric acid. GlycocoU. 

If a small quantity of uric acid be gently heated with nitric 
acid in a porcelain capsule, it is dissolved with a disengagement 
of red vapors, and the solution, evaporated at a gentle heat, 
leaves a residue which assumes a purple color on the addition 
of a drop of ammonia. 

This test is characteristic of uric acid, and permits the de- 
tection of the least traces of that substance. The purple body 
formed is called murexide. 

2b pp 53 



626 ELEMENTS OP MODERN CHEMISTRY. 

DERIVATIVES OF URIC ACID. 

Among the numerous compounds which may be derived from 
uric acid, some are closely related to oxalic acid, or other acid 
containing two carbon atoms ; others are derived from mesoxalic 
acid (see farther on), which contains three carbon atoms. All 
of these derivatives are more or less closely related to urea ; they 
are substituted ureas, and are more specially designated by the 
name ureides. Those related to mesoxalic acid are the more 
direct derivatives. 

Alloxan, C'H^N^O*.— This body is one of the products of 
the oxidation of uric acid by nitric acid ; urea is formed at the 
same time. 

C^HWO^ + H^O + O =: C^H^N^O* + CH^N^O 

Uric acid. Alloxan. Urea. 

It may be prepared by introducing uric acid, in successive 
small quantities, into nitric acid of a density of 1.41-1.42, as 
long as it dissolves producing red vapors. The alloxan finally 
separates in a mass of delicate needles ; in about twenty-four 
hours they are drained and dissolved in water at 60 or 65°. 
On cooling, the alloxan separates in voluminous crystals con- 
taining 4 molecules of water of crystallization. They efilo- 
resce in dry air. 

When crystallized from a hot solution, alloxan forms rhombic 
octahedra, containing but a single molecule of water. 

It is very soluble in water, and the solution is acid. By the 
action of alkalies, baryta-water for example, alloxan is con- 
verted into alloxanic acid^ which is formed by the direct com- 
bination of the elements of one molecule of water with alloxan. 

C^H^N^O* -f H^O = C^HWO^ 

Alloxan. Alloxanic acid. 

The alloxanates are decomposed by boiling into mesoxalic 
acid and urea. Thus if a solution of alloxanic acid, or even 
alloxan, be added to a boiling solution of lead acetate, a precipi- 
tate of lead mesoxalate is formed. 

Q4JJ4N205 _|_ H^O = Q'O'W + CH^N^O 

Alloxanic acid. Mesoxalic acid. Urea. 

Mesoxalic acid, C=^0\OH)'^ = CO.OH-CO-CO.OH, is a 
dibasic acid. According to Baeyer, its diatomic radical, mes- 
oxalyl, exists in alloxan itself, which is mesoxalylurea, that 
is, urea in which two atoms of hydrogen are replaced by the 
diatomic radical [(CO)^-C(OH)^]''. 



DERIVATIVES OF URIC ACID. 627 

p^^NH2 p^^NH-C0^p.^TTX2 p^^NH-C202-CO.OH 

Urea. Mesoxalyl-urea Alloxanic or 

(alloxan). mesoxaluric acid. 

Dialuric Acid, C*H*N^O*, is the product of the prolonged 
action of hydrogen sulphide on a hot solution of alloxan or 
alloxantin. 

Alloxan. Dialuric acid. 

It is also formed by the action of sodium amalgam on the 
same solutions. 

It crystallizes in long needles, quite soluble in water ; these 
crystals assume a red color in the air, and are gradually trans- 
formed into alloxantin. 

When a solution of alloxan is added to a solution of dialuric 
acid, alloxantin is formed. 

Dialuric acid. Alloxan. Alloxantin. 

Baeyer regards dialuric acid as tartronyl-urea, that is, urea 
in which two atoms of hydrogen are replaced by the diatomic 
radical of tartronic acid. 
CO.OH 

^^■^^ co<^^' co<'^H-^^-^ro ro<'NH-co^p„^„ 

CO.OH ^^^NH2 ^^^NH-CO>^^ CO<^j^jj_(,q>CH.OH 

Tartronic acid. Urea. Alloxan. Dialuric acid 

(tartronyl-urea). 

Barbituric Acid, C*H*N^Ol— This acid, which is malonyl- 
urea, is formed by the action of nascent hydrogen on dibrom- 
alloxan. 

CO<NH-CO> '^^'^ + 2H' = 2HBr + CO<^|:^g>CH' 

Dibromalloxan. Barbituric acid. 

It crystallizes in large prisms, slightly soluble in cold and more 
soluble in boiling water. Ebullition with alkalies converts it 
into malonic acid and urea. 

Malonyl-urea. Malonic acid. Urea. 



Alloxan, dialuric and barbituric acids, which have been de- 
scribed, are ureides derived from a single molecule of urea by 
the substitution of the radical of a dibasic acid for two atoms 
of hydrogen. The groups C^O^[(CO•^-C(OH)'^],C^O^-CH.OH, 



628 ELEMENTS OF MODERN CHEMISTRY. 

C^O^-CH^, wliich in oxalic, mesoxalic, tartronic, and malonic 

acids are united to two hydroxyls, are diatomic. 

CO.OH CO.OH CO.OH 

C(0H)2 CH(OH) CH2 

CO.OH CO.OH CO.OH 

Mesoxalic acid. Tartronic acid. Malonic acid. 

^^<NH:cO>^(^I^)' CO<^g:g^>CH.OH CO<^H-CO^(.jj, 

Mesoxalyl-urea Tartronyl-urea Malonyl-urea 

(alloxan). (dialuric acid). (barbituric acid). 

The following compounds are diureides; they are derived 
from two molecules of urea in which four atoms of hydrogen 
are replaced by two dibasic acid radicals, each of which contains 
three atoms of carbon and is related to mesoxalyl : 

Alloxantin, C^H^N^O^ — This body is produced by the re- 
duction of alloxan. When a current of hydrogen sulphide is 
passed through a cold solution of alloxan, sulphur separates, 
and a crystalline precipitate of alloxantin soon forms. 

2C*H2N20* + H^S = C«HWO^ + H'^'O + S 

Alloxan. Alloxantin. 

Alloxantin is also formed directly, at the same time as 
alloxan, by the action of weak nitric acid on uric acid. It 
crystallizes in small, colorless prisms containing 3 molecules 
of water of crystallization. It is but slightly soluble in cold 
water. Nitric acid converts it into alloxan, and reducing agents 
transform it into dialuric acid. 

Purpuric Acid and Murexide. — Scheele had already ob- 
served murexide, which Prout studied and described as pur- 
purate of ammonia. It is, indeed, the ammonium salt of a 
nitrogenized acid, C^H^N^O^, for which it is convenient to pre- 
serve the name purpuric acid (Beilstein). 

Murexide is formed by the action of ammonia on dry allox- 
antin heated to 100°, or again, when ammonia or ammonium 
carbonate is added to a hot solution of alloxantin or alloxan. 

C^HWO^ _|_ 2NH3 = C^H*(NIP)N^O« + H^O 

Alloxantin. Murexide (ammonium purpurate). 

Murexide crystallizes in quadrangular prisms, or in tables 
which are green by reflected and red by transmitted light. 
These crystals, which contain one molecule of water, present 
the magnificent metallic reflections shown by the wings of can- 
tharides. They dissolve in water with a rich purple color. 

Allantoin, C*H«N*Ol— This body was discovered in 1800, 



DERIVATIVES OF URIC ACID. 629 

by Vauquelin and Buniva, in the allantoic liquid of the cow, 
that is, the urine of the foetal calf. It occurs also in the urine 
of young calves. In 1836, Liebig and Wohler obtained it by 
oxidizing uric^ acid with lead dioxide. Gorup-Besanez has 
observed its formation in the action of ozone upon uric acid. 

Grimaux has made the synthesis of allantoin by heating 
one part of glyoxylic acid with two parts of urea, for eight or 
ten hours. 

Q2H2Q3 ^ 2(CH^N^0) = C^HWO^ + 2H20 

Glyoxylic acid. Urea. Allantoiu. 

From this remarkable synthesis, it appears that allantoin is 
derived from two molecules of urea ; it is the diureide of gly- 
oxylic acid. 

Allantoin may be prepared by boiling uric acid with water, 
and adding lead dioxide, in small quantities, as long as that 
oxide continues to be converted into a white powder, which is 
lead carbonate. The filtered liquid, freed from lead by hydro- 
gen sulphide, yields crystals of allantoin on evaporation. 

Uric acid. Allantoin. 

Allantoin crystallizes in brilliant, colorless prisms. It dis- 
solves in 30 parts of boiling water and in 160 parts of cold 
water ; it is also soluble in alcohol, but is insoluble in ether. 
It forms crystallizable compounds with certain metallic oxides. 



The following compounds are ureides of oxalic and glycollic 
acids : 

Parabanic Acid, C^H^N^Ol— This body is formed by the 
action of an excess of nitric acid on alloxan, which thus gives 
up the elements of carbon dioxide. 

Alloxan. Parabanic acid. 

Parabanic acid forms thin, transparent prisms, which are 
very soluble in water. By boiling with acids, it is transformed 
into oxalic acid and urea. Baeyer regards it as oxalylurea. 

NH-CO 

When parabanic acid is heated with ammonia, ammonium 
oxalurate is formed, and separates in fine needles. In this 
case the parabanic acid is converted into oxaluric acid by 
directly combining with the elements of water. 

53* 



630 ELEMENTS OF MODERN CHEMISTRY. 

Parabanic acid. Oxaluric acid. 

It is seen that oxaluric acid is related to parabanic acid, as 
alloxanic acid is to alloxan. 

Hydantoin, or Glycolyl Urea. — The relations between this 
compound and parabanic acid are the same as those between 
glycollic and oxalic acids. It is glycolyl urea, C^H^N^O'^ and 
is formed by the action of hydriodic acid on allantoin. 

MTJ_nTT2 

C^HWO^ _|_ 2HI = C0< X + CON^O* 4- P 
^NH-CO ^ 

Allantoin. Hydantoin. Urea. 

It crystallizes in needles, fusible at 215°, very soluble in hot 
water. Its solution is neutral. When hydantoin is heated with 
baryta- water, it is converted into hydantoic acid. 

Q3JJ4jy^2Q2 _|_ J12Q ^ C^H^N^O^ 

Hydantoin. Hydantoic acid. 

Hydantoic Acid, C^H^N^O^ may be obtained synthetically 
by heating urea with glycocoll ; ammonia is disengaged. 

^^<NH2 + 6H2-CO.OH ^ ^^<NH-CH2-C0.0H + ^^' 

Urea. Glycocoll. Hydantoic acid. 

Indeed, hydantoic acid is formed by the replacement of one 
atom of hydrogen in urea by the group CH^-CO.OH, which is 
acetic acid less one atom of hydrogen. 

It crystallizes in large, rhomboidal prisms, soluble in water. 
It is monobasic. When heated with hydriodic acid it is con- 
verted into glycocoll. 

C0<^5^' „2 ^„ _„ + H20 = C02 + NH3 + ^^"^ 

^NH-CH2-C0.0H ^ CH2-C0.0H 

Hydantoin and hydantoic acid present evident relations with 
parabanic and oxaluiic acids. 

^^^NH-CO rn^NH2 

CC>< j^jj_(i,Q ^^^NH-CO-CO.OH 

Parabanic acid. Oxaluric acid. 

^^<-^Yl-bo ^^^NH-CH2-C0.0H 

Hydantoin. Hydantoic acid. 

We cannot further continue the study of the numerous de- 
rivatives of uric acid. This study has already thrown much 
light upon the constitution of the acid, without definitely de- 
termining it. The syntheses indicated by Horbaczewski (page 



CREATINE — CREATININE. 631 

625), and by Behrend and Roosen, as well as more recent 
investigations of E. Fischer, afford additional proof for the 
correctness of the formula of uric acid given above, 

DERIVATIVES OF GUANIDINE. 

There are interesting structural relations between urea and 
guanidine ; the latter is urea in which the oxygen is replaced 
by the imidogen group NH. 

CO<gg C(NH)<«g 

Urea, Guanidine. 

This analogy is borne out in the guanidine derivatives corre- 
sponding to the ureides just described. 

Hydantoin, or glycolyl-urea, corresponds to a glycolyl-guani- 
dine which has been named glycocyamidine. 

^ NH-CO ^ NH-CO 

Hydantoin, Glycocyamidine. 

Hydantoic or uracetic acid corresponds to a guanidine acetic 
acid called glycocyamine. 

^^\NH-CH2-C0.0H ^^ ~^^NH-CH2-C0.0H 

Hydantoic or uracetic acid. Glycocyamine or guanidine- 

acetic acid. 

Glycocyamine is formed by the mixture of aqueous solutions 
of glycocoll and cyanamide. 

^^NH CH2-NH2 ^^^ n^^H2 

<m + 60.OH ' HI.=C<NH-CH2-C0.0H 

Cyanamide, Glycocoll, Glycocyamine. 

Our space only permits the mention of these bodies, but we 
must describe their important homologues, creatine and creati- 
nine, which have long been known. 

CREATINE AND CREATININE. 

Creatine results from the direct combination of cyanamide 
and methylglycocoll (sarcosine), a reaction discovered by Vol- 
hard, and entirely analogous to that which yields glycocyamine 
(see above). 

^^NH CH2-NH(CH3) ^^ ^NH2 

^^NH + CO.OH = HN=C<N(CH3)-CH2-CO.OH 

Cyanamide, Methylglycocoll. Creatine, 

Creatinine, or methylglycocyamidine, results from the dehy- 
dration of creatine. 



632 ELEMENTS OF MODERN CHEMISTRY. 

™=C<^HJg3)_cH2-CO.OH = H^O - HN=C-NH-CO 

N(CH3)-CH2 
Creatine. Creatinine. 

Creatine, C^H^N^O^ + H^O.— This body was discovered hy 
Chevreul in meat broth. It exists ready formed in the muscles, 
and passes into tlie extract of meat. It may be prepared by 
treating the solution of this extract with basic acetate of lead, 
filtering, freeing the filtrate from excess of lead by hydrogen 
sulphide, and evaporating the solution at a gentle heat until it 
crystallizes. The crystals are separated from the mother-liquor, 
and alcohol added to the latter precipitates a fresh quantity of 
creatine (Neubauer). 

Creatine crystallizes in brilliant, colorless, oblique rhombic 
prisms, containing one molecule of water, which they lose at 
100°, becoming opaque. 

By the action of acids or by long boiling with water, crea- 
tine is converted into creatinine. 

Creatine. Creatinine. 

When creatine is boiled with baryta-water, it is converted 
into sarcosine, ammonia being disengaged and barium carbon- 
ate precipitated at the same time. It is generally considered 
that the ammonia and carbon dioxide are produced in this case 
at the expense of urea, which is formed directly by the decom- 
position of creatine. 

Creatine. Sarcosine. Urea. 

Sarcosine is methylglycocoll (page 603), isomeric with lac- 
tamide and alanine. 

Creatinine, C^H'N^O. — This body exists in muscular tissue 
independently of creatine. It may be precipitated from the 
mother-liquor from which the latter body has deposited, by 
adding an alcoholic solution of zinc chloride, which forms a 
crystalline combination with the creatinine. 

Creatinine crystallizes in oblique rhombic prisms. It is much 
more soluble in alcohol than creatine. It has basic properties^ 
and forms a crystallizable compound with hydrochloric acid. 

Creatine and creatinine have been found not only in the 
muscles, but in small quantities in the brain, blood, and urine, 



ERYTHRITOL. 633 

POLYHYDRIC ALCOHOLS. 

The only tetrahydric alcohol of importance is erythritol, 
and rhamnitol represents the pentahydric alcohols. 

The best characterized hexahydric alcohol is mannitol, a 
sweet, crystallizable substance, which is extracted from 
manna. Glucose is related to mannitol, from which it differs 
only by two atoms of hydrogen. The constitution of man- 
nitol may be expressed by the following formula : 
Q6HU06 ^ C«H«-(OH)« 

It appears from the experiments of Linnemann that various 
saccharine matters, possessing the composition C^H^^O®, fix H'^ 
directly under the influence of sodium amalgam and water, 
and are converted into mannitol. The latter body is charac- 
terized as a hexahydric alcohol by the property which it pos- 
sesses of forming neutral compounds with 6 molecules of a 
monobasic acid, such as acetic acid. In other words, this 
body contains 6 hydroxyl groups, or six atoms of hydrogen 
capable of being replaced by 6 monobasic acid radicals. 

Six isomeric alcohols of the composition C^H"0^ are known, 
and theory indicates the possible existence of fourteen. 

ERYTHRITOL. 

This beautiful body was discovered in 1849 by Stenhouse, 
who found it among the decomposition products of erythric 
acid or erythrin, a substance contained in certain lichens. 
In 1852, Lamy obtained from an alga, the Protococcus vul- 
garis, a substance which he first named phycite, but which 
he afterwards recognized to be identical with erythritol. 

Preparation. — De Luynes first extracts erythrin from a 
lichen, the Rocella Montagnei, and decomposes it, while still 
moist, by slaked lime in closed vessels at a temperature of 
150°. Under these conditions, erythrin is decomposed into 
carbonic acid which is at once taken up by the lime, orcinol, 
and erythritol, which are separated by crystallization, the 
orcinol being deposited first. The erythritol is purified by 
washing with ether, which removes a trace of orcinol. 

Properties. — Erythritol crystallizes in tetragonal prisms. 
The crystals are hard, have a feeble, sweet taste, and are very 



634 ELEMENTS OF MODERN CHEMISTRY. 

soluble in water, soluble in boiling absolute alcobol, and insol- 
uble in ether. They melt at 126°. Erythritol reacts with 
the acids, forming neutral bodies analogous to the ethers 
(Berthelot). 

When heated with a concentrated solution of hydriodic 
acid, it is converted into secondary butyl iodide (de Luynes.) 

C^jjioQ* ^ 7HI = C*H«I -f 4:W0 + 3P 

Erythritol. Secondary butyl iodide, 

MANNITOL. 

C6H1106 = C6H8(OH)6 

This body, discovered by Proust in 1806, exists in a great 
number of vegetables. It is the most abundant constituent 
of manna, a substance which flows from several species of ash, 
either naturally or from incisions. It is prepared by dis- 
solving manna in distilled water, in which the white of an egg 
has previously been beaten up. The solution is boiled several 
minutes and then filtered through a woollen cloth and allowed 
to cool. The liquid then solidifies to a mass of crystals which 
are purified by recrystallization after treatment with animal 
charcoal. 

Mannitol forms large, right rhombic prisms. Its taste is 
sweet, and it is soluble in water and hot alcohol. 

When heated with a concentrated solution of hydriodic 
acid, it is reduced to a secondary hexyl iodide. 

C6H1406 + llHI = CH3-CH2-CH2-CHI-CH2-CH3 + GH^O + SP 
Mannite. jS-secondary hexyl iodide. 

It forms a hexacetate, a hexanitrate, and a hexastearate. 
By oxidation with nitric acid it yields mannose, an aldehyde, 
and fructose, a ketone. 

There are several stereoisomers of mannitol. 

Bulcitol, C®II'*0^, which has been obtained from Madagas- 
car manna, exists in certain plants, such as Melampyrum 
nemorosum and Evonymus europxiis. It forms large, oblique 
rhombic prisms, and is less soluble in water than mannitol ; 
it is but slightly soluble in alcohol. It melts at 188.5°. Like 
its isomer, mannitol, it is reduced by hydriodic acid to a 
secondary hexyl iodide. 

Sorbitol, C^ff^O", obtained by J. Boussingault from the 
fermented juice of the mountain-ash, is another isomer of 
mannitol. 



AND CELLULOSES. 635 

It forms small acicular crystals containing water of crys- 
tallization. Hydriodic acid reduces it to normal secondary 
hexyl iodide. Sorbitol has been obtained from glucose by 
reduction. 

Perseitol, C^H^^O'^, or Mannoheptitol, is a beptahydric alco- 
hol which occurs in the leaves and berries of Laurus persea, 
and has been synthetically prepared from mannose ; it crys- 
tallizes in microscopic needles, melting at 188°. 



SUGARS, STARCHES, AND CELLULOSES. 

Among the more widely distributed products of the vege- 
table kingdom must be included the various kinds of sugar, 
starch, the gums, and the matter of young vegetable cells, or 
cellulose. 

These compounds contain carbon, hydrogen, and oxygen in 
such proportions that the oxygen is present in exactly sufficient 
quantity to form water with the hydrogen. Their composition 
is then expressed by the general formula ^"(H^O)". If all of 
the oxygen and hydrogen were removed in the form of water, 
only carbon would remain. Hence the name hydrates of car- 
bon^ often applied to this class of bodies. 

They can be arranged in three different classes, of which 
the types are glucose, saccharose, and starch. 

The first of these, termed monosaccharides, comprises a 
number of aldehyde alcohols (aldoses) and ketone alcohols 
(ketoses) ; their molecules contain a carbonyl group (CO) 
and several hydroxyl (OH) groups. According to the num- 
ber of oxygen atoms contained in the molecule, they are 
designated trioses, tetroses, pentoses, hexoses, etc. The second 
class, embracing di- and trisaccharides, may be considered to 
be ether-like anhydrides of the monosaccharides, formed by 
the condensation of two or more molecules of the latter, with 
elimination of the elements of one or several molecules of 
water. Hydrolysis resolves them into their monosaccharide 
components. The known disaccharides are all derived from 
the hexoses ; according to the number of monosaccharide 
molecules that can be obtained from them, they are distin- 
guished as hexobioses, hexotrioses, etc. 



636 



ELEMENTS OF MODERN CHEMISTRY. 



The 'polysaccharides, to whicli starch and cellulose belong, 
are very different in their physical properties from the sugars : 
they are non-crystalline and insoluble. They yield sugars 
by hydrolysis, but their molecules are much more complex 
than those of the disaccharides. 



MONOSACCHARIDES. 

Glycerose, C3H603 
Erythrose, C4H804 
Arabinose, C5H1005 
Xylose, C5H10O5 
Rhamnose, C6H1205 
(Man nose, C6HI206 
Aldoses^ Glucose, C6H12O6 

(Galactose, C6H12O8 
Ketose \ Fructose, C6H12O6 



DI- AND TRI-SACCHARIDES. POLYSACCHARIDES. 

Saccharose, C12H2201i Starch, (C6Hi0O6)n 

Lactose, C12H22011 Inulin, (C6Ui0O5)n +H20 

Maltose, CI2H22011 Glycogen, (C6HiOH5)n 

Isomaltose, C12H22011 Cellulose, (C6Hioo5)n 

Blelitose, C18H32016 Dextrin, (C6Hi0O6)n 

Melizitose, CiSHSSQie Gums, (C6Hioo5)n 



ARABINOSE. 



C5H10O5 = CH2.0H-[CH.0H]=^-CH0 

This is the sugar of gum. It is formed when arabin, or 
gum arable, is boiled with dilate nitric acid. It crystallizes 
in brilliant rhomboidal prisms, fusible at 160°. Its aqueous 
solution has a sweet taste and is dextrogyrate. It reduces 
Fehling's solution, but is not fermentable. By an interesting 
but complicated process arabinose can be obtained from glucose 
(Wohl). 

Xylose i& stereoisomeric with arabinose. It is obtained by 
heating wood-gum with dilute sulphuric acid. 

Rhamnose, C^H^^O^, is another pentose. It contains a 
methyl group, and results from the hydrolysis of certain 
glucosides. 

Mannose, C^H^^O^ = CH10H-[CH.0H]*-CH0. — Man- 
nose was first obtained as a product of the oxidation of man- 
nitol (Fischer). It has since been observed among the sub- 
stances which result from the hydrolysis of certain naturally 
occurring hydrates of carbon, such as reserve-cellulose. Man- 
nose forms friable masses which are very soluble in water, 
difficultly soluble in alcohol, and insoluble in ether. It is 
dextro-rotatory, and fermentable with brewer's yeast. With 
phenylhydrazine it yields a characteristic and difficultly crys- 
tallizable compound, C^'H^sN'O^ melting at 195°. With an 
excess of phenylhydrazine, it yields the same product as 
glucose and fructose, — normal phenylglucosazone. Nascent 
hydrogen converts mannose into mannitol, and bromine water 
oxidizes it into mannonic acid. It must, therefore, be re- 
garded as the aldehyde of mannitol. 



GLUCOSE. 637 

aLUCOSE. 

C6H1206 

This important body, wliicli forms the solid and crystalliza- 
ble part of honey, exists in a great number of dried fruits, on 
the surface of which it forms a well-known white efflorescence. 

It is also found in the urine in the disease known as diabetes. 

It may be made artificially by the action of dilute sulphuric 
acid on starch (Kirchoff), or on cellulose (Braconnot). 

Its synthesis was achieved when it was obtained by reduction 
of the lactone of gluconic acid (E. Fischer). 

Preparation. — Gllucose is prepared in the arts by the fol- 
lowing process : 

6000 litres of water and 42 kilogrammes of sulphuric acid 
are introduced into a large wooden trough, and the liquid is 
heated by jets of superheated steam. When it is in full ebul- 
lition, 2000 kilogrammes of starch suspended in 2000 litres 
of warm water are allowed to run in gradually, and in thirty 
or forty minutes the saccharification is complete. The sul- 
phuric acid is then saturated with pulverized chalk, the insol- 
uble calcium sulphate is separated, and the liquid concentrated 
in boilers heated by steam until it marks 40 or 41° Baume. 
It is then allowed to crystallize, and solidifies to an opaque, 
yellowish, crystalline mass, which is glucose. 

The sulphuric acid has recently been replaced by hydrochlo- 
ric acid, which produces a whiter product. The small quantity 
of calcium chloride formed does not prevent the crystallization 
of the glucose. 

Properties. — This body crystallizes in small, white, rounded 
masses, agglomerated like cauliflowers. The crystals contain 
one molecule of water of crystallization (C*'H^'^0*' -}- H^O). 
They remain unchanged in the air. They melt when heated 
on a water-bath, and lose their water at 100°. Anhydrous 
glucose, deposited from alcoholic solution, melts at 146°. 

Grlucose dissolves in a little more than its own weight of 
water at 17°. It is three times less soluble than cane-sugar, 
and in solutions of equal concentration it is three times less 
sweet. It is much less soluble in alcohol than in water. 

The solution of glucose rotates the plane of polarization to 
the right. The deviation caused by a recently-prepared solution 
diminishes after a time as much as fifty per cent. ; it varies with 
the concentration. The specific rotatory power is [a]D = 52.6°. 

54 



638 ELEMENTS OF MODERN CHEMISTRY. 

A levo-form and an inactive variety of glucose are also 
known. 

Griucose forms true compounds with the bases. There is a 
glucosate of calcium^ C^H^°Ca''0^ + H^O. It is precipitated 
when alcohol is added to a solution of calcium hydroxide in an 
aqueous solution of glucose. The glucosates are not stable : 
carbonic acid decomposes them, regenerating glucose. 

If potassium hydroxide be added to a solution of glucose 
and the liquid be heated, it first becomes yellow, and then 
rapidly assumes a deep-brown color. Ordinary or cane-sugar 
does not produce this reaction, and can thus be distinguished 
from glucose. 

The action of lime on glucose gives rise to the formation 
of a substance which forms beautiful crystals of the ortho- 
rhombic type, and which Peligot called saccharin.^ It is 
dextrorotatory, has a bitter taste, and melts at 160°. Accord- 
ing to Scheibler, it contains C^H^^O^ and is the anhydride of 
a saccharinic acid, C^H^^O^. 

Griucose reduces various metallic solutions. Gold and silver 
are precipitated by it from their solutions. If a solution of 
cupric sulphate be poured into a solution of glucose, and 
potassium hydroxide be added, no precipitate is formed, but 
the liquid acquires a dark-blue color. On heating it, a red 
precipitate of cuprous oxide is formed. 

This reaction, which was discovered by Troemmer, is very 
sensitive, and can be used for the detection of the smallest 
quantities of glucose. In making the test an alkaline copper 
solution, known as FeliUng^s solution, is employed. It is 
best prepared by dissolving separately 34.6 grammes of crys- 
tallized copper sulphate, and 173 grammes of Eochelle salt 
and 60 grammes of caustic soda, each in half a litre of water, 
and mixing equal volumes of these solutions when the test is 
to be made. The quantity of glucose can be determined by 
titration with this solution, for one molecule of sugar reduces 
exactly five molecules of cupric oxide. 

When a solution of glucose is heated with bismuth nitrate 
and an excess of potassium hydroxide, a black precipitate of 
reduced metallic bismuth is formed. 

* This substance must not be confounded with saccharine, or benzoic acid 
sulfinide, C6H*<[p^ ]>NH, which is a derivative of benzene, and, owing 
to its intensely sweet taste, is sometimes used as a substitute for sugar. 



FRUCTOSE, OR LEVULOSE. 639 

Grlucose is one of the aldoses, being at the same time a 
pentahydric alcohol and an aldehyde. Its constitution is 
represented by the formula 

CHIOH-CH.OH-CH.OH-CH.OH-CH.OH-CHO 

This is deduced from the following facts : acetic anhydride 
converts glucose into a pentacetyl derivative, showing it to 
contain five hydroxyl groups ; its reducing properties are due 
to the presence of an aldehyde group, which is shown by its 
oxidation to gluconic acid, CffOH-(CH.OH)*-COOH, and 
its reduction by nascent hydrogen to mannitol, a primary alcohol. 
It is confirmed by the behavior of glucose with hydroxyl- 
amine and with phenylhydrazine. With one molecule of the 
latter reagent, it yields the hydrazone CHIOH(CH.OH)*- 
CH=N^H-C^H^, but upon heating with an excess of phenylhy- 
drazine, phenylglucosazone, CH^0H(CH.0H)^-C(N2HC''H^)- 
CH=N•^C^H^ is produced. 

Galactose, C^H^^O^. — This is one of the products of the 
action of dilute acids and of certain ferments on lactose 
(page 644). Galactose crystallizes in little masses, formed 
by the agglomeration of small needles. It is less soluble in 
water than glucose, and deviates the plane of polarization to 
the right. It is fermentable, and readily reduces cupro- 
potassic solutions. Nascent hydrogen converts it into dul- 
citol. Nitric acid oxidizes it with formation of mucic acid. 



FRUCTOSE, OR LEVULOSE. 
C6H1206 = CH2.0H-CH.OH-CH.OH-CH.OH-CO-CH20H 

Besides the glucose which effloresces on their surface after 
desiccation, many fruits contain another sugar, which strongly 
deviates the plane of polarization to the left. It is fructose, 
formerly known as levulose. 

Fructose exists in inverted sugar (page 643). Many sweet 
fruits contain inverted sugar ; among them are grapes, cher- 
ries, figs, gooseberries, etc. 

The extraction of fructose from inverted sugar — of which 
it constitutes one-half — is a laborious procedure. Dubrunfant 
recommends the conversion of the sugars into their calcium 
compounds : the fructosate of calcium is difficultly soluble 
in water, while the glucosate is readily dissolved. A better 



640 



ELEMENTS OF MODERN CHEMISTRY. 



metliod of preparing fructose consists in warming inulin witli 
dilute acids. For this purpose a few drops of sulphuric acid 
are added to a solution of inulin in water and the liquid 
heated gently for some time. The sulphuric acid is then 
precipitated with barium hydrate and the filtrate evaporated. 
Upon adding a crystal of fructose, the fruit sugar separates 
in colorless acicular crystals. It may be purified by recrys- 
tallization from alcohol. 

Fructose thus obtained contains no water of crystalliza- 
tion ; the crystals belong to the orthorhombic system. It 
melts at 95°, and is readily soluble in water and in alcohol. 
The fructose contained in inverted sugar rotates the plane 
of polarization to the left, and rather more strongly than 
the other component, glucose, turns it to the right ; for this 
reason inverted sugar is slightly levorotatory. 

A fructose which is optically inactive, but agrees in all 
other respects with the natural product, has been artificially 
obtained by E. Fischer. He has further succeeded in con- 
verting this into mannose and glucose, and in resolving it into 
its dextro- and levo-rotatory modifications. Thus the synthesis 
of the most important monosaccharides has been accomplished. 

Fructose is directly fermentable. Its reactions closely re- 
semble those of glucose, except that on oxidation it does not 
yield an acid with the same number of carbon atoms, but is 
resolved into tartaric and glycollic acids. This proves that 
fructose is a ketone. 

Sorbinose, C^H^^O^, a substance which crystallizes in large, 
transparent rhomboidal octahedra, has been obtained from 
the berries of the mountain-ash by Pelouze. It appears to 
be stereoisomeric with the fructoses. 



SACCHAROSE, OR CANE-SUGAR. 

Q12II220n 

Extraction. — Ordinary sugar, which is widely distributed 
in the vegetable kingdom, is extracted principally from sugar- 
cane, sugar-maple, and beet-root. Fresh sugar-cane contains 
about 18 per cent, of sugar, and beet-roots from 12 to 16 per 
cent. 

Certain sweet fruits contain cane-sugar, independently of 
inverted sugar. According to Buignet, such are apricots, 
peaches, pine-apples, lemons, plums, and raspberries. 



SACCHAROSE. 641 

We can only briefly indicate the processes wliicli are em- 
ployed for the extraction of sugar from beet-root. 

The roots are washed, and reduced to pulp in a machine 
provided with a cylinder armed with teeth and having a rapid 
rotary motion. This pulp is then strongly pressed in woollen 
sacks by means of a hydraulic press, and the juice is imme- 
diately transferred to large boilers having double bottoms and 
heated by steam, and milk of lime is added. 

This operation, which is called clarification^ is intended not 
only to separate certain substances which form insoluble com- 
pounds with the lime, but to prevent the juice from becoming 
altered by reason of its acidity. As the sugar itself dissolves 
a large quantity of lime, the latter must be got rid of. A cur- 
rent of carbon dioxide is consequently passed into the solution, 
and decomposes the saccharate of calcium. Another process 
for removing the excess of lime depends on the employment 
of ammonium phosphate. Insoluble calcium phosphate is 
formed, and the ammonia is disengaged on account of the high 
temperature at which the operation is conducted. By this 
process the neutralization is more perfect. 

The liquid is then heated to about 95°, and filtered through 
a layer of animal charcoal in grains ; it is then concentrated in 
evaporating-pans heated by steam. When the syrup marks 
25° Baume, it is again filtered through animal charcoal, and 
the concentration is finished in pans heated by steam, and in 
which a vacuum is maintained during the evaporation. The 
cooking of the syrup is thus carried on at a temperature not 
above 75 or 80°, and these conditions assure a fine quality of 
product and a good yield by preventing as much as possible 
the transformation of the sugar into uncrystallizable sugar. 

When the syrup marks 42 or 43°, it is run into cooling- 
pans, where it is continually stirred until the sugar is depos- 
ited in small crystals. These are distributed in moulds, which 
consist of terra-cotta cones having a hole in the summit, which 
for the time is closed. These cones are placed in an oven 
heated to 25°, where the crystallization takes place ; when the 
syrup has solidified, the holes in the cones are opened and the 
thick and colored mother-liquor is allowed to drain out ; it con- 
stitutes molasses. The loaves of sugar, drained and dried, are 
delivered to commerce as crude or brown sugar. 

For some years an apparatus has been used for draining 
and bleaching of crude sugars, which consists of a cylindrical 
qq 64* 



642 ELEMENTS OF MODERN CHEMISTRY. 

cage having perforated metallic walls. It is put into rapid 
motion on its axis, and the molasses is expelled through the 
perforated walls by centrifugal force. The apparatus is called 
the centrifugal drier. 

Refining^ of Crude Sugar. — The crude sugar is crushed, 
sifted, and dissolved in about 30 per cent, its weight of water, 
the operation being conducted in a boiler heated by steam. 5 
per cent, of animal charcoal is then thrown into the hot solu- 
tion, and, after stirring, i per cent, of beefs blood is added. 
The latter coagulates in the liquid and envelops all of the sus- 
pended particles, uniting them in a scum which is easily re- 
moved. When the liquid becomes clear, it is drawn off and 
filtered. It is then passed through grained animal charcoal, 
which completely decolorizes it. It is concentrated in vacuum- 
pans, from which it is drawn into a large copper vessel having 
a double bottom. It is continually stirred until crystallization 
commences, after which it is run into moulds, which are then 
placed in rooms heated to 20°. After the crystallization is 
completed, the syrup remaining liquid is allowed to drain out. 

At the termination of the draining, a creamy mixture of 
white clay and water is poured on the surface of the sugar in 
each mould, and the water of this broth slowly penetrates the 
mass of sugar, liquefies the syrup which remains between the 
crystals, and carries it to the lower part of the mass. The clay, 
having lost its water, contracts, dries up, and remains upon the 
decolorized sugar as a dry cake. It is removed, and a syrup 
of white sugar is run into the whitened and porous loaf and 
fills up all of the spaces when it solidifies in the oven. 

This operation, the object of which is the decolorizing of 
the sugar-loaves, is called claying. The clay broth may be 
replaced by syrup of white sugar, an operation which is called 
decoloring. 

The sugar solidified in the moulds is a compact, crystalline, 
white mass, composed of little grains. It may be obtained in 
voluminous crystals by concentrating the syrup until it marks 
3*7° Baume, and then exposing it for some days to a tempera- 
ture of 30° in copper vessels, across which threads are stretched. 
The sugar is deposited on the threads in large crystals known 
as rock-candy. 

Properties of Sugar. — Sugar crystallizes in large, oblique 
rhombic prisms, having hemihedral facettes. The crystals are 
hard, anhydrous, and unalterable in the air. Density, 1.606. 



SACCHAROSE. 643 

It dissolves in one-third its weight of cold water ] the solution 
is thick, and is known as simple syrup. Sugar is insoluble in 
ether and in cold absolute alcohol. Boiling absolute alcohol 
dissolves a little more than one per cent. ; ordinary alcohol will 
take up more. The aqueous solution of sugar deviates the plane 
of polarization to the right, ([a]D = -f 66.5°), at 20°. 

At 160°, sugar melts to a thick, transparent liquid, which 
solidifies to an amorphous, vitreous mass on cooling. 

¥/hen maintained for a long time at a temperature of 160 
or 161°, it breaks up into glucose and levulosan (Grelis). 
(.12^22011 ^ C^H^^O^ + C^H^oQ^ 

Saccharose. Glucose. Levulosan. 

Between 190 and 200° it loses the elements of water and is 
converted into a bitter, brown, amorphous mass, which is desig- 
nated as caramel. 

Cane-sugar does not reduce alkaline copper solutions, and 
does not react with phenylhydrazine. 

Inverted Sugar. — By the action of dilute acids, sugar is 
converted, slowly in the cold and rapidly on boiling, into a 
mixture, in equal proportions, of two isomeric sugars which 
have opposite rotatory powers : they are glucose and fructose. 
The mixture is called inverted sugar. 

Q12H22Q11 _|_ JJ2Q ^ C^H^^O^ + C^H^^O^ 
Saccharose. Glucose. Fructose. 

The same transformation is efi"ected by the soluble matter 
of yeast (Berthelot), and also, according to Buignet, by the 
action of the peculiar ferments which exist in most fruits. 

Sugar only ferments after having first undergone this trans- 
formation into inverted sugar by the action of the ferment. 

Nitric acid converts sugar into saccharic acid., C^H^^O®, and 
oxalic acid. 

Concentrated sulphuric acid carbonizes it. 

Saccharose resists the action of alkalies better than glucose. 
It forms with them and with the bases in general, definite com- 
binations known as saccharates. 

If a mixture of sugar and slaked lime be triturated with 
water and the whole be thrown upon a filter, the liquid which 
passes through will be colorless and strongly alkaline. When 
it is heated to ebullition, it changes into a solid mass which 
again becomes liquid on cooling. It is a solution of saccharate 
of calcium, (C^^H'''^0^^)^3CaO. Alcohol precipitates from it the 
compound C^^H^^qh (j^^q^ 



644 ELEMENTS OF MODERN CHEMISTRY. 

An excess of strontium hydrate precipitates cane-sugar 
completely from a hot solution ; the resulting disaccharate, 
Q12JJ22Q11 2gj.Q^ is readily decomposed by carbon dioxide into 
sugar and strontium carbonate. Scheibler has founded a 
process for extracting crystallizable sugar from molasses upon 
these reactions. 

When sugar is fused with potassium hydrate, it disengages 
hydrogen, and carbonate, oxalate, formate, acetate, and pro- 
pionate of potassium are formed. 

When distilled with quick-lime, sugar is decomposed with 
formation of carbon dioxide, water, acetone, and metacefone, 
C^H'O, a liquid having a pleasant odor and boiling at 84°. 

Sugar forms a crystalline compound with sodium chloride. 

LACTOSE, OR MILK-SUaAR. 

This sugar exists in solution in the milk of mammals, and is 
extracted from the whey which remains after the manufacture 
of cheese. It is only necessary to evaporate this liquid to 
crystallization. 

Milk-sugar occurs in commerce in cylindrical masses, formed 
of an agglomeration of crystals around a little stick which 
serves as a nucleus. The crystals are colorless, hard, and creak 
when crushed by the teeth. They are right rhombic prisms, 
terminated by octahedral points. They contain one molecule 
of water of crystallization which they lose at about 140°. 
They dissolve in 6 parts of cold, and in 2 parts of boiling 
water. The solution turns the plane of polarization to the 
right. The rotatory power of old solutions is [a]D = +52.53°. 

When heated with nitric acid, lactose yields certain acids, 
•among which is one which is but slightly soluble in water, 
and which is called mucic acid. It contains C^H^^O^, and is 
stereoisomeric with saccharic acid, which is also produced by 
the oxidation of lactose by nitric acid. Moderate oxidation 
with bromine water converts lactose into lactobionic acid, 
Qi2jj22Qi2^ which upon warming with dilute acids yields 
galactose and gluconic acid. 

When boiled with dilute sulphuric acid, milk-sugar is con- 
verted into glucose and galactose. 

Milk-sugar reduces cupro-alkaline solutions, but more 
slowly than glucose. 



MALTOSE. 645 

With phenylhydrazine it yields phenyllactosazone, C^*H'^ 
N*0*, yellow needles melting at 200°. When exposed to the 
air at summer heat, a solution of lactose in presence of calcium 
carbonate soon undergoes the lactic fermentation (page 647). 

MALTOSE. 

This name is given to the crystallizable sugar produced, 
together with dextrin, by the action of diastase on starch. 
It may be prepared by digesting starch paste at 60° with a 
solution of diastase. The solution is precipitated by alcohol, 
which separates the dextrin, filtered, the alcoholic liquid 
evaporated to a syrupy consistence, more alcohol added, and 
the solution set aside to crystallize over sulphuric acid. Mal- 
tose is a product of the incomplete hydration of starch. 

Maltose forms masses composed of hard, white needles. 
It loses its water at 100°. Its solution turns the plane of 
polarization to the right, [a]D = -\-137°. It reduces 
Fehling's solution, and when boiled with dilute acids is con- 
verted into glucose. Maltose is directly fermentable. Heated 
with acetic anhydride and sodium acetate, it yields an octo- 
acetyl derivative, C'^Hi*0^(O.CO.CH=*)^ and with an excess 
of phenylhydrazine it gives phenylmaltosazone, C^^H^WO^ 

Isomaltose, C^^H^^O^^, is formed by the action of hydrochloric acid 
upon glucose, and from starch in presence of diastase. It has an 
intensely sweet taste, and is dextrorotatory to about the same extent 
as maltose. It is decomposed upon gentle heating, but does not 
seem to be directly fermentable. 

Mycose, or trehalose, Ci^H^^O^^ -\- 2W0, was extracted by Mitsch- 
erlich from the ergot of rye, and has been obtained by Berthelot 
from a Turkish manna (trehala). It crystallizes in hard, rectan- 
gular octahedra, gritty between the teeth, and having a sweet taste. 
It is strongly dextrogyrate, [a]D = -|-199°. It is distinguished from 
cane-sugar by its ready solubility in boiling alcohol. 

Melitose, or raffinose, C^^H^^Qie _|_ 5H^0, was extracted by Berthe- 
lot from Australian manna, a sweet exudation of the eucalyptus, 
and is known to exist in sugar-beets. Being more soluble than 
ordinary sugar, it accumulates in the molasses. It crystallizes in 
fine needles which lose their water of crystallization at 100°, while 
the residue melts at 118°. Melitose is powerfully dextrorotatory, 
[a]D z= 104.4°, a property which interferes with the estimation of 
ordinary sugar by polarimetry when both are present. It does not 
react with Fehling's solution, but is completely fermentable. On 
hydrolysis, it yields fructose, glucose, and galactose. 



646 ELEMENTS OF MODERN CHEMISTRY. 

Melezitose, Ci»H320i6 + 2H20, was obtained by Berthelot from 
Brian9on manna, exuded by the larch {Pinus larix). It crystallizes 
in monoclinic prisms, with two molecules of water, which it loses 
at 108°. It is dextrogyrate, [a]D = -f 94°. It melts at 157°. Its 
complete hydrolysis yields only glucose. 

FERMENTATION. 

, If yeast be introduced into a tolerably concentrated solution 
of glucose, and the liquid be exposed to a temperature between 
20 and 30°, bubbles of an incombustible gas will soon be dis- 
engaged, and this gas will produce a cloud in lime-water. It 
is carbon dioxide. 

After the disengagement of gas has ceased, a small quantity 
of alcohol may be obtained by distilling the liquid. 

In this experiment, the glucose disappears ; it is broken up 
into alcohol and carbon dioxide. The decomposition is effected 
by yeast, and is called fermentation. The sugar is the fer- 
mentable substance ; the yeast is \hQ ferment. 

The ferment is an organized matter which develops and mul- 
tiplies at the expense of the glucose. The latter, is directly at- 
tacked by this being which lives at its expense, and undergoes a 
complete decomposition, of which carbon dioxide and alcohol 
are the principal products. The ferment plays an active part, 
which was first suspected by Cagniard-Latour and Schwann, 
and demonstrated by Pasteur. 

Alcoholic Fermentation. — The decomposition of glucose 
under the influence of yeast constitutes the alcoholic fermenta- 
tion. 

The principal reaction is expressed in the following equa- 
tion: 

Q6JJ1206 ^ 2C^H«0 + 2C0' 

Glucose. Alcohol. 

It is shown by the experiments of Pasteur, that only 94 per 
<;ent. of the quantity of glucose decomposed undergoes the 
change indicated by the above formula. The remaining 6 per 
cent, are employed: 1, in the formation of small quantities 
of higher alcohols, succinic acid, and glycerol ; 2, in the de- 
velopment of new yeast cells. 

Yeast is composed of a mass of cells or ovoid corpuscles, 
having a diameter of y^ of a millimetre, and arranged in 
clusters (Pig. 129). Their walls are an elastic membrane, 
and their contents are liquid or granular. They contain cellu- 
lose, albuminoid matter, and mineral salts. When they are 




FERMENTATION. 647 

introduced into a substance which contains the materials neces- 
sary for their development, they multiply rapidly. Pasteur has 
made decisive experiments on this point. He planted some 
yeast cells in a solution of sugar to which he had added a small 
quantity of an ammoniacal salt and some phosphates. The solu- 
tion of sugar fermented, and the ferment developed by budding, 
the new cells absorbing the 
ammonia and the phosphates. 
They obtained from the sugar 
the matter necessary to form 
cellulose, and from the ammo- 
nia the nitrogen required for 
the elaboration of the albumi- 
noid matters. However, these 
artificial conditions are not 
those which are best adapted 
for the propagation of the cells. 
The latter increase with ex- 
treme energy in liquids which 
contain, besides the yeast, glu- 
cose, and a small quantity of Ficf* 129. 
albuminoid matter ready formed. 

Lactic Fermentation. — This fermentation, of which the 
conditions have already been indicated (page 597), is accom- 
plished by the action of a peculiar ferment of vegetable char- 
acter. It is formed of small round or elongated cells, very 
short, and isolated, or in masses. They are much smaller than 
yeast cells, and constitute the lactic yeast of Pasteur. It only 
acts upon glucose or lactose in a neutral or alkaline liquid. 
Hence the necessity of adding sodium carbonate or chalk to 
the liquid. The reaction consists in a splitting of the glucose 
molecule. 

(;J6JJ12Q6 ^ 2C^H«0^ 

Glucose. Lactic acid. 

Butyric Fermentation. — This consists in the transforma- 
tion of calcium lactate into butyrate, — a transformation that is 
accompanied by a disengagement of hydrogen. According to 
Pasteur, this fermentation is caused by a low organism which 
can live and thrive only in situations where its members can- 
not obtain free oxygen. Such is the energy of their respira- 
tory functions that free oxygen kills them (Pasteur). They 
decompose oxidized bodies and assimilate the oxygen. 



648 



ELEMENTS OF MODERN CHEMISTRY. 



We have already considered the acetic fermentation. "We 
may add that by the action of a certain ferment, glucose is 
converted into mannitol and a gummy matter, very soluble 
in water, and which gives a viscous consistence to the fer- 
mented liquid. This is called the viscous fermentation. 

There are many other kinds of fermentation, an exceed- 
ingly large number of carbon compounds being capable of 
decomposition in this manner; the ferments are also very 
numerous, and the special fermentation undergone by a sub- 
stance depends upon the peculiar ferment present. 

Fermented Beverages. — The foregoing summary indi- 
cations regarding fermentation may be supplemented by some 
general notions upon the fermented beverages wine and beer. 

Wine. — It is universally known that wine is the product 
of the fermentation of grape-juice. This juice contains in 
solution inverted sugar, small quantities of gummy matters, 
vegetable albumen, a trace of fatty matters, coloring matters, 
free tartaric and malic acids, and various tartrates, princi- 
pally potassium acid-tartrate, or cream of tartar. 

The clarified wine which results from the fermentation of 
this juice consists of an aqueous solution of various products, 
some of which existed in the juice, and others which are the 
result of the transformation through which it has passed. 
Among the first are the mineral and vegetable salts of the 
juice (in smaller proportion, because they are partly deposited 
with the lees), the gummy matter, a small quantity of fatty 
and albuminoid substances, the coloring matters, free tartaric 
and malic acids, and the tannin derived from the grape-stems 
and from the skins and seeds. 

Among the substances which result from the fermenta- 
tion are : 

1. Alcohol, which is the principal product. 

2. Carbonic acid gas ; still wines retain but a small propor- 
tion, the fermentation taking place entirely in open vessels, but 
sparkling wines contain it abundantly under pressure, the final 
fermentation having taken place in the bottle after corking. 

3. Small quantities of aldehyde and acetic acid produced by oxi- 
dation of the alcohol. The acetic acid reacts upon the alcohol con- 
tained in the wine, forming acetic ether. 

4. Grlycerol and succinic acid, in small quantities (Pasteur). 

5. Traces of compound ethers, which contribute to the bouquet 
of the wine. Besides acetic ether, traces of a compound ether called 
Knanthic ether have been found in wine ; it appears to be pelargonic 



FERMENTATION. 64Q 

ethffr, C9H"02(C2H5). Berthelot states the existence of but slightly 

volatile acid ethers (malic, tartaric) in wine. 

The following table indicates the quantities by volume of pure 

alcohol contained in 100 volumes of various wines : 

California Port 22.00 

Madeira 20,48 

Port 20.22 

Sherry 18.00 

Sauterne (white) 15.00 

Catawba 13.00 

Rhine Wines 11.11 

California Riesling 11.20 

Champagnes 11.00 to 18.00 

Strong Clarets 8.00 to 12.00 

Light Clarets 7.5 to 8.00 

Red Burgundy 7.66 

Red Macon 7.66 

White Burgundy 7.83 

Beer. — Beer is a fermented beverage, made from a wort of 
germinated barley, and ordinarily rendered aromatic by bops. 
Like all other cereals, barley contains a considerable proportion 
of starch. During the germination, this starch is partially con- 
verted into maltose by the action of a nitrogenized matter, 
which is formed in the sprouting grains, and which is called 
diastase. In order to saccharify the barley, it is then first 
necessary to cause it to germinate, and for this purpose it is 
moistened with water, and kept for some time at 
a temperature of 14 or 15° ; the object of this 
operation, called malting, is the development of ^ ^^ 

the diastase necessary for the saccharification - V^^ 
of the starchy matter. When the sprout has /T>) MW\)) 
acquired about the same length as the grain 
(Fig. 130), the germination is arrested by ex- In 

posing the malt to the action of a temperature \\|^ 

of about 50°. The dry malt is then reduced 
to a coarse powder, placed in a large vat, and Fig. 130. 
brewed for about three hours with water heated 
to 50 or 60°. In this operation, the diastase of the malt con- 
verts the starch into dextrin and maltose, which dissolve, to- 
gether with the other soluble principles of the grain. 

The sweet wort thus obtained is heated with hops, which 
yield to it their essential aromatic oil. It is then properly 
cooled and allowed to ferment in deep vats, into which a cer- 
tain quantity of yeast produced in a previous operation is in- 
troduced at the same time. The alcoholic fermentation soon 
begins and goes on with great activity during a few days. As 
2c 55 




650 ELEMENTS OF MODERN CHEMISTRY. 

soon as it has ceased, the liquid can be delivered for consump- 
tion. The quality of beer is better when the fermentation 
takes place at a low temperature. 

Beer contains much water, free carbonic acid gas, alcohol (2 
to 5 per cent.), variable quantities of saccharine matters, dex- 
trin, nitrogenized matters, extractive, bitter, and coloring mat- 
ters, essential oil, and various salts. Ale and porter are in 
nature analogous to beer, but are relatively richer in alcohol 
and nitrogenous and extractive matters. 

STARCH. 

(C^HioOS)" 

Starch is universally diffused throughout the vegetable king- 
dom. It is especially abundant in the seeds of leguminous 
plants and cereals, and in the potato. 

Extraction. — To extract starch from potatoes, they are re- 
duced to pulp by means of a rasp, and the pulp is placed in a 
sieve and washed by a stream of water. The water carries 
with it the fine granules of starch, while the torn cells of the 
potato remain in the sieve. The starch gradually deposits 
from the water, and collects in the bottom of the vessel, where 
it settles, forming a cake from which the supernatant water 
may be separated by decantation. 

Starch may be extracted from wheat by making a paste of 
flour and kneeding it in a sieve under a jet of water : the starch 
granules are carried with the water, and a soft, gray, elastic 
mass remains in the sieve, constituting the nitrogenized matter 
of the flour, or gluten. 

Another process, almost abandoned at present on account of 
its offensiveness, consists in allowing the coarsely-ground grain 
to putrefy. Putrefaction destroys the gluten, while the starch 
resists decomposition. 

Physical Properties. — Starch is a white powder, formed of 
granules which present an organized structure. Their size and 
shape are variable (Fig. 131), their diameter being from 2 to 185 
thousandths of a millimetre. Those of potato starch are larger 
than those of starch from grain. These granules are made up 
of concentric layers, which are more dense as they are nearer 
the surface. It is easy to make this structure apparent by 
causing the granules to undergo a partial disintegration by the 
action of hot water. They swell up, burst open, and separate 
into thin layers, as shown in Fig. 132. 



STARCH. 



651 



Chemical Properties. — Starch is insoluble in water, alcohol, 
and ether. Contact with water heated to 60 or 70° causes it 
to swell up considerably, without dissolving. A semi-trans- 
parent, gelatinous mass results, which is known as starch paste. 
When starch is boiled with a large quantity of water and the 
whole is thrown on a filter, the liquid which passes is slightly 
turbid, and constitutes an emulsion of starch. It contains 
in suspension flakes of amylaceous matter small enough to 
pass through the filter. It also contains a small quantity 
of soluble starch (see farther on). 

If a few drops of solution of iodine be added to the emul- 
sion, a deep-blue color is at once produced. This blue color 
disappears when the liquid is heated to 90°, and reappears 
on cooling. The compound contains about 18 per cent, of 
iodine, and is known as " iodide of starch" ; its constitution 
is unknown. The reaction serves as a delicate test both for 
starch and iodine. 





Fig. 131. 



Fig. 132. 



Metamorphoses of Starch — Dextrin. — When long heated 
to 100° starch is converted into soluble starch, which yields a 
blue color with iodine (Maschke). 

Between 160 and 200° it is converted into a body which is 
very soluble in water, and the solution of which is not colored 
by iodine. This solution strongly turns the plane of polariza- 
tion to the right ; hence the name dextrin given to this body, 
which is regarded as isomeric with starch, (C^H^°0^)". A very 
concentrated solution of dextrin has the appearance of a solu- 
tion of gum. It is ased as a mucilage for labels and postage- 
stamps, and for the preparation of immovable surgical dress- 
ings. 



652 ELEMENTS OF MODERN CHEMISTRY. 

Alcohol added to a solution of dextrin precipitates the latter 
substance in the form of flakes. Subacetate of lead does not 
precipitate dextrin, a character which permits the latter body 
to be distinguished from gum arabic. 

When starch is boiled with water containing a few per cent, 
of sulphuric acid, it is first converted into dextrin, then into 
glucose. It is generally considered that the dextrin is formed 
by a simple molecular transformation of the elements of thq 
starch, and that the glucose is then produced by the simple 
fixation of one molecule of water. 

starch. Glucose. 

According to Musculus, this is not the case ; but soluble 
starch is the result of a metameric transformation of starch, 
and subsequently is converted into dextrin and glucose by a 
true decomposition. 

3C6H10O5 _[_ H^O = C^^H^oQ'" + C^H^^O^ 

starch. Dextrin. Glucose. 

By the prolonged action of the acid, the dextrin itself is 
converted into glucose. 

The transformation of starch into dextrin and saccharine 
matter (maltose) takes place easily under the influence of a 
peculiar ferment which is developed in grain during germina- 
tion, and to which the name diastase has been given. It 
may be obtained by precipitating aqueous extract of malt by 
alcohol. 

If starch be triturated with one and a half times its weight 
of concentrated sulphuric acid, avoiding an elevation of tem- 
perature, and the mixture be left to itself for half an hour and 
alcohol then added, a substance is precipitated which is soluble 
in water and assumes a rich blue tint by the action of iodine. 
It is soluble starch (Bechamp). 

Starch dissolves abundantly in monohydrated nitric acid, 
and water precipitates from this solution a white substance, 
which, after washing and drying, constitutes xyloldin. It is 
mononitrate of starch, and is formed by the following reaction : 

Q6H10O5 _^ HNO^ = H^O -h C^H^(NO^)0* 

starch. Xyloidin. 

Xyloidin burns with deflagration when heated to 180°, 
A dinitrate has also been obtained. 



INULIN — aLYCOGEN — GUMS. 653 

INULIN. 

This body also is largely diffused tlirougliout the vegetable 
kingdom. It exists in the roots of the elecampane {Inula 
helenmm), chicory, and Spanish chamomile, in the bulbs of 
colchicum, the tubers of the dahlia, in the Jerusalem arti- 
choke, etc. It may be extracted from the tubers of the dahlia 
by reducing them to a pulp and washing the latter in a sieve 
under a stream of water. The milky Hquid which passes 
through deposits the inulin, which consists of granules analo- 
gous to those of starch. It swells in cold water, in which it 
is very slightly soluble. It is very soluble in boiling water, 
which again deposits it in a pulverulent form on cooling. The 
aqueous solution turns the plane of polarization to the left. 
It is not colored blue by iodine, which communicates to it a 
fugitive, yellow-brown tint. 

By long boiling with water, or by the action of dilute acids, 
inulin is converted into fructose, and this reaction affords a 
convenient mode of preparing fruit-sugar. 

GLYCOGEN. 

(C6Hi'>05)'i 

This body, isomeric with cellulose and starch, exists in the 
animal economy. Claude Bernard discovered it in the liver, 
and afterwards in the placenta. It exists also in many organs 
during the foetal life. Nearly pure glycogen may be obtained 
by adding a large quantity of crystallizable acetic acid to a cold 
and concentrated decoction of liver. It is also precipitated 
when alcohol is added to an aqueous decoction of liver. In a 
pure state, it is a white, amorphous powder. When dried in 
the air, it has the composition CW^O^ (E. Pelouze). At 100° 
it loses one molecule of water. 

With water it forms an opalescent liquid. Alcohol and 
ether do not dissolve it. Boiling with dilute acids converts it 
into glucose. Iodine communicates to it a violet or brown-red 
color. 

GUMS. 

By the names gums and mucilages are understood certain 
substances existing everywhere in the vegetable kingdom, and 
which dissolve or swell up in water, giving a mucilaginous 

65* 



654 



ELEMENTS OF MODERN CHEMISTRY. 



consistence to the liquid. The gums proper are distinguished 
from the mucilaginous substances, which are not really soluble. 
Both furnish mucic and oxalic acids when treated with nitric 
acid. Hydrolysis decomposes them into hexoses and pentoses 
(galactose, arabinose, xylose). 

Gum Arabic. — Grum arabic is identical with Senegal gum. 
It flows naturally from different species of acacia. It dissolves 
abundantly in cold water and is precipitated from its solution 
by alcohol. Fremy considers that it is composed essentially of 
the calcium and potassium salts of an acid which he designates 
as gummic acid (arahin). 

When dried at 100°, the latter body has the composition 
indicated by the formula C^^H^^O^^ It is very soluble in 
water, and its solution rotates the plane of polarization to the 
left. 

When heated to 120-150°, it becomes insoluble in water 
and is converted into metagummic acid. According to Fremy, 
the gum of cherry- and plum-trees is a mixture of gummates, 
which are soluble in cold water, and insoluble metagummates. 
The metagummates are insoluble in water, but when boiled 
with that liquid are transformed into soluble gummates. 

Subacetate of lead forms an abundant white precipitate in 
solutions of gum arabic. 

When gum arabic is boiled with dilute sulphuric acid, it is 
converted into saccharine substances; some varieties of this 
gum yield considerable quantities of galactose when treated in 
this manner, while others are largely converted into arabinose. 
On oxidation with nitric acid, the former give mucic 'acid, and 
the latter oxalic acid. 

Gum Tragacanth. — This gum flows from the Astragalus of 
the Levant and of Persia. Bassora gum is derived from a spe- 
cies of cactus. Both contain a mucilaginous matter insoluble in 
water, but which swells up in that liquid, forming a transparent 
jelly. This matter is hassorin. With nitric acid, it yields much 
mucic acid. When boiled with dilute sulphuric acid, it is readily 
converted into crystallizable glucose. 

CELLULOSES. 

The frame-work of plant tissues consists of a more or less 
delicate membrane which is a secretion of protoplasmic ac- 



CELLULOSES. 655 

tivity, and is known as the cell-wall. In the earlier stages 
of its growth and development this consists of cellulose^ 
(C^H^^O^)", with a varying amount of water. Gradually, 
however, it is transformed into bodies of more complex con- 
stitution, — the compound celluloses^ — and, at the same time, 
mineral matters are deposited in it. 

The term cellulose does not denote a chemical individual, 
but a group of closely related isomers of similar properties. 
Cotton, hemp, flax, and the pith of certain trees consist 
essentially of cellulose. Wood, cork, and mucilage are chiefly 
made up of the compound celluloses produced by the meta- 
morphosis of cellulose. All these bodies are permeated by 
foreign substances, such as nitrogenous, coloring, and mineral 
matters ; the latter are found more or less modified in the 
ashes. 

Old linen and cotton serve for the preparation of pure 
cellulose. Such materials are boiled with a weak solution of 
potassium hydrate, washed, and successively exhausted with a 
solution of chlorine, acetic acid, alcohol, ether, dilute hydro- 
chloric acid, dilute hydrofluoric acid, and, finally, water, and 
dried at 100°. The undissolved residue is pure cellulose. 

Properties. — Cellulose is a diaphanous, white solid, of a 
density of 1.5. It is insoluble in all simple solvents, but in 
presence of certain metallic compounds it forms gelatinous 
hydrates which are soluble in water. It dissolves completely 
upon warming with concentrated aqueous solution of zinc 
chloride, more rapidly and in the cold when a solution of 
the salt in strong hydrochloric acid is employed (Cross and 
Bevan). Another valuable solvent for cellulose is cupram- 
monium hydroxide dissolved in strong ammonia water 
(Schweitzer's reagent) ; this rapidly converts cellulose into 
a hydrate, which is gradually dissolved in the blue liquid. 
Salts of the alkali metals, acids, alcohol, etc., reprecipitate 
the hydrate. 

When submitted to dry distillation, cellulose leaves a resi- 
due of carbon and yields numerous gaseous and liquid prod- 
ucts. The gas obtained by the distillation of wood is used for 
illuminating purposes in some localities. The liquid product 
ordinarily separates into two layers, one of which is aqueous 
and contains acetic acid, wood-spirit, acetone, etc. ; the other 
is insoluble in water and constitutes wood-tar. 

Cellulose is readily attacked by cencentra*ted sulphuric 



656 ELEMENTS OP MODERN CHEMISTRY. 

acid : the resulting viscous solution probably contains a com- 
pound of sulphuric acid and cellulose, and also various other 
products resulting from a rapid disintegration of this sul- 
phate. When the solution is diluted with water and boiled, 
glucose is formed and sulphuric acid regenerated. Certain 
celluloses yield mannose instead of glucose. 

C6JJ10O6 _^ H^O = C^H^^O^ 

Cellulose. Glucose. 

When paper is dipped into a cold mixture of sulphuric acid 
with half its volume of water, and is then carefully washed 
and dried, a semi-transparent matter is obtained which has a 
certain rigidity, and is similar to parchment in aspect and 
toughness. This parchment paper is extensively used as a 
substitute for animal parchment. 

Colloidal cellulose is formed by the action of sulphuric 
acid of density 1.53 on cellulose, and forms with water a 
milky liquid which can be filtered. The action of sulphuric 
acid or zinc chloride on cellulose produces a body analogous 
to starch and called amyloid. Cellulose moistened with iodine 
tincture and then treated with strong sulphuric acid becomes 
blue. By treatment with acetic anhydride, cellulose has 
been converted into the triacetate CH^O'CC'H^O')^ and the 
tetracetate C*'H^O(C'^H^O^)*, and there are indications that 
higher acetates may exist. 

Gim-Cotton. — When carded cotton is immersed for half a 
minute in monohydrated nitric acid, and then rapidly washed 
in a large quantity of water and allowed to dry in the air, a 
substance is obtained which possesses all the exterior appear- 
ances of cotton, but is very inflammable and burns suddenly 
without residue. It is gun-cotton, or pyroxylin^ which was 
discovered by Schonbein in 1847. 

In its preparation, the monohydrated nitric acid may be 
advantageously replaced by a mixture of one volume of nitric 
acid (sp. gr. 1.5) and three volumes of sulphuric acid. The 
duration of the action determines the composition of the prod- 
uct. When the acid is allowed to act upon the cotton for a 
short time only, the latter is converted into a mixture of the 
compounds, C^'H^«(NO=*)^0« and C^■'H^XNO0^O^ but upon con- 
tinued treatment with the acids a gun-cotton of the composi- 
tion C^'^H^XNO^'O* results. 

These bodies, like nitroglycerin, are true nitric ethers. Alka- 
lies decompose them into an alkaline nitrate and cellulose. 



ELEMENTS OF MODERN CHEMISTRY. 657 

Grun-cotton looks like cotton, but is more harsh to the touch. 
It burns with a flash, leaving no residue, and produces a great 
volume of gaseous products consisting of carbon monoxide, 
carbon dioxide, nitric oxide, etc., and vapor of water. The 
hexanitrate is insoluble in water, alcohol, ether, and the cupro- 
ammoniacal solution. The lower nitrates, however, are soluble 
in a mixture of ether and alcohol, and collodion is essentially 
such a solution : it is used in surgery and photography. 

Celluloid, a substitute for ivory, bone, and horn, is made 
by dissolving nitrocellulose in melted camphor, to which 
resinous substances and coloring matters are sometimes added. 

Nitro-powders, largely used on account of their smokeless 
explosion, are prepared by gelatinizing finely divided gun- 
cotton by means of a solvent such as ethyl acetate or acetone. 
The solvent is removed by pressure and evaporation, and the 
gelatinous residue is cut into slices or pressed into suitable 
form. Other substances are usually added to modify the 
force of the explosion. 

GLUCOSIDES. 

The glucosides are complex compounds, which break up 
under various conditions, fixing the elements of water and 
yielding a sugar, generally glucose, and other bodies, just as 
the compound ethers, in fixing the elements of water, are de- 
composed into alcohols and acids. 

Various immediate principles of vegetable origin can be 
classed as glucosides. We may mention particularly the foh 
lowing : 

6LTJC0SIBES. FORMULAS. ORIGIN. 

Amygdalin .... C''20H27N011 bitter almonds. 

Salicin C^3jji807 willow and poplar bark. 

Populin C20H22O8 bark and leaves of the aspen. 

Phloridzin .... C2iH240io bark and roots of fruit-trees. 

Arbutin C^^hi^OT leaves of the Arctostaj^hylos uva utsi. 

Esculin C21H24013 bark of India chestnut. 

Quercitrin .... C^^H^soso bark of Quercus tin ctoria (quercitron). 

Tannin , C'*H28022 oak-bark, nut-gall, etc. 

Coniferin CI6H22O8 cambium of the Coniferse. 

Digitalin C'^H^soiz leaves of Bigitah's purpurea. 

Amygdalin, C'^H^^NO".— This body is extracted from the 
cake of bitter almonds, and it deposits from its alcoholic solu- 
tion in crystals containing two molecules of water. Its aqueous 
solution allows it to crystallize in quite large crystals contain- 
ing three molecules of water 
rr 



658 ELEMENTS OF MODERN CHEMISTRY. 

Amygdalin is very soluble in water and in boiling alcohel. 
Its aqueous solution rotates the plane of polarization to tbe 
left. 

By the action of dilute acids amygdalin is decomposed into 
hydrocyanic acid, benzaldehyde (oil of bitter almonds), and 
glucose. 

C20H2^NO" -I- 2H20 =: CWO + CHN + 2C«Hi20^ 

Amygdalin. Benzaldehyde. Hydrocyanic Glucose. 

acid. 

The same decomposition takes place by the action of water 
and a peculiar ferment which is contained in both bitter and 
sweet almonds, and which is called emulsin, or synaptase. It 
is a nitrogenized matter, soluble in water, and only acts on 
amygdalin in presence of water. It is well known, indeed, that 
bitter almonds only develop the odor of prussic acid when 
moistened with water. 

Salicin, C^^H^^O^ — Salicin exists already formed in the bark 
of the willow and poplar. Wohler discovered its existence in 
castoreum. It may be prepared by exhausting willow-bark 
with boiling water, concentrating the liquid and digesting it 
with litharge. The solution is then filtered and evaporated to 
a syrupy consistence ; the salicin deposits in a few days. 

It occurs in small scales, or brilliant needles, soluble in water 
and alcohol and insoluble in ether. Its taste is bitter. 

By the action of a solution of emulsin (the nitrogenous mat- 
ter of almonds), it breaks up into a neutral body called salige- 
ninol, and glucose. 

Q13JJ1807 _|_ H^O = Q'WO' + C^H^^O^ 

Salicin. Saligeninol. Glucose. 

Dilute sulphuric and hydrochloric acids decompose it by 
the aid of heat into saliretin and glucose. 

By the action of a mixture of potassium dichromate and 
sulphuric acid, salicin yields carbon dioxide, formic acid, and 
an oxidized oil, which is salicylaldehyde, C^H^O'^ (Piria), 

Salicin has been obtained synthetically (Michael). 

Populin, C'°H^20'-f 2H'''0.— Braconnot discovered this sub- 
stance in the bark and leaves of the aspen (Popuhts tremula). 
When properly purified, it occurs in very fine, silky, colorless 
needles. Its taste is sweet ; it is but slightly soluble in water, 
more soluble in alcohol. By the action of dilute acids it is 
decornposed into benzoic acid, saliretin, and glucose ; the latter 



GLUCOSIDES. 659 

two products result from tlie decomposition of salicin, so that 
populin is a combination of benzoic acid and salicin, from 
whicb substances it has also been obtained artificially. 

Q20U22Q8 _J_ JJ^O = C^H«0' + C^^H^^O' 

Populin. Benzoic acid. Salicin. 

Phloridzin, C'^^H^^O^" + 2H20.— This substance exists in 
the bark of apple, pear, plum, and cherry trees, and principally 
in the roots of fruit-trees. 

When pure, it forms colorless, silky needles, having a bitter 
taste, and an after-taste which is sweet. It is scarcely soluble 
in cold water, but dissolves abundantly in boiling water and 
in alcohol. The alcoholic solution turns the plane of polariza- 
tion to the left. 

Dilute acids decompose it into phloretin and glucose. 

Q21JJ24O10 _^ H^O = C'^H"0^ -f C^H^^O^ 

Phloridzin. Phloretin. Glucose. 

PJdoretin is a white substance which crystallizes in little 
scales, slightly soluble in water and very soluble in alcohol. 
When phloretin is heated with potassium hydroxide, it breaks 
up into phloretic acid and 'phloroglucinol (page 696). 



Q15HU05 


+ 


H^O 


= (TWO' + Q'WO' 


Phloretin. 






Phloretic acid. Phloroglucinol. 



Coniferin, C^^H^^O^, is a glucoside which occurs in the 
cambium of the Coniferse. It is a crystalline body which melts 
at 185°, and effloresces in the air. On treatment with boiling 
dilute acids or with emulsin, it yields glucose and coniferyl 
alcoliol^ C^°H^^O"', a substance from which vanillin^ the essen- 
tial principle of the vanilla bean, can be obtained by oxidation. 

Digitalin, C^^H^^O^l — This is an amorphous body which 
may be extracted from the leaves of Digitalis purpurea and 
lutea. When treated with concentrated hydrochloric acid, it 
yields glucose and various complex bodies. Owing to the 
peculiar efi"ect it produces on the contractions of the heart, it 
is of great medicinal value. 

Tannin, or Tannic Acid, C^*B[^°0^ — The names tannins 
and tannic acids are applied to certain slightly acid com- 
pounds which are largely diffused in the vegetable kingdom, 
and which have two important properties : they precipitate 
solutions of gelatin and albuminous matters, and produce a 



660 ELEMENTS OF MODERN CHEMISTRY. 

bluisli or greenisli-black color with the ferric salts. The most 
important of these compounds is the tannin of oak bark, or 
quercitannic acid. It was formerly considered a glucoside : 
according to Strecker, it has the composition C'^H'^^0^^, and 
yields glucose upon treatment with dilute acids. 

(.34JJ28022 _^ 4H2Q _ 4C^H«0^ + C«H^^O« 
Taunin, Gallic acid. Glucose. 

More recent researches of Schiff render it probable, how- 
ever, that pure tannin is digallic acid, C^*H^°0^, the anhydride 
of gallic acid (see page 713). 

Tannin exists in oak bark, in sumac, and in large quan- 
tities in nut-galls, which are excrescences developed by the 
sting of an insect on the leaves and branches of the Quercus 
infectoria. 

It is prepared by introducing coarsely-powdered nut-galls into 
a percolator, and exhausting them with ordinary commercial 
ether. The ethereal solution which passes through is collected 
in a flask, and in the course of a day separates into two or 
sometimes three layers. The lower layer is a very concen- 
trated, aqueous solution of tannin. It is separated and dried 
in a hot-air oven. The tannin remains as a light, bulky mass, 
having a yellowish color. 

Tannin is a colorless, amorphous solid, having a very astrin- 
gent taste. It is very soluble in water, less soluble in alcohol, 
insoluble in pure ether. 

On contact with the air, the aqueous solution of tannic acid 
absorbs oxygen, disengages carbon dioxide, and deposits gallic 
acid. This transformation takes place more rapidly when oak 
tannin is boiled with dilute sulphuric or hydrochloric acid. 

A solution of tannic acid produces with ferric salts a bluish- 
black precipitate, which constitutes ink. Tannin does not color 
ferrous salts, but the mixture soon blackens on exposure to the 
air by absorbing oxygen. 

Tannin is employed in medicine as an astringent. Nut-galls, 
which are very rich in tannin, are used for the manufacture of 
ink. A good ink may be prepared by the following receipt: 
One kilogramme of powdered nut-galls is exhausted with 14 litres 
of water ; the solution is filtered, and a solution of 500 grammes 
of gum arable is first added, then a solution of 500 grammes of 
ferrous sulphate (green vitriol). The mixture is well stirred 
up, and then exposed to the air until it has acquired a fine 
black color. 



ACIDS DERIVED FROM THE SACCHARINE BODIES. 661 

ACIDS DERIVED FROM THE SACCHARINE 
BODIES. 

By moderate oxidation (careful treatment witli bromine 
water) the sugars containing the aldehyde group are con- 
verted into the corresponding monobasic acids. The most 
important of these are mannonic acid, gluconic acid, and 
galactonic acid. They are derived from hexoses and have 
the composition C^H^^O^ 

When subjected to a more energetic oxidizing action (nitric 
acid or excess of bromine water), the saccharoses and their 
corresponding monocarboxylic acids yield dibasic acids. Of 
these we may mention the four isomers represented by the 
formula C^H^°0^, — namely, mannosaccharic acid, saccharic 
acid, mucic acid, and isosaccharic acid. 

The relations which exist between these acids and the 
sugars from which they are derived afford valuable indica- 
tions regarding the constitution of the hydrates of carbon. 



Mannonic Acid results from the oxidation of mannose. 
It forms a syrupy liquid which readily passes into a crystal- 
line anhydride (lactone) by the loss of a molecule of water. 

Gluconic Acid is obtained from glucose by oxidation with 
bromine water. It is stereoisomeric with the preceding. 
Upon evaporation of its solution it remains as a syrup, which 
gradually deposits crystals of its lactone. 

Galactonic Acid corresponds to galactose, and may be 
prepared from milk-sugar. It has been obtained crystallized ; 
its lactone is also known. 

Mannosaccharic Acid is the dibasic acid resulting from 
the oxidation of mannose or mannonic acid. When its aqe- 
ous solution is evaporated, it loses two molecules of water and 
is converted into the corresponding lactone. 

Saccharic Acid is produced together with oxalic acid 
when cane-sugar is oxidized by nitric acid. It is also formed 
by the oxidation of sorbitose, glucose, and gluconic acid. 
Free saccharic acid is a thick liquid, which solidifies upon 
standing owing to the formation of its lactone, C^H^O^ The 
acid potassium salt is sparingly soluble in cold water. 

Mucic Acid was discovered by Scheele in 1780. It is 
66 



662 ELEMENTS OF MODERN CHEMISTRY. 

prepared by the oxidation of milk-sugar with nitric acid. 
It may also be obtained from dulcitol, galactose, and galac- 
tonic acid. It forms a white crystalline powder which melts 
at 213°, and is but sparingly soluble in cold water. By boil- 
ing with water it is converted into a lactonic acid. By dry dis- 
tillation it is converted into pyromucic acid, C^H*0^ (p. 746). 

PECTIC MATTERS. 

These bodies, of which the constitution is still obscure, are 
largely diffused in the vegetable world, notably in fleshy fruits 
and in many roots. They remain in a gelatinous condition 
on evaporation of their aqueous solutions, from which they 
can be precipitated by alcohol. They are probably related 
to the hydrates of carbon. 



AROMATIC COMPOUNDS. 

The compounds of carbon which we have thus far con- 
sidered may be regarded as derived from methane, CH*, and 
the great majority of them may be obtained from this hydro- 
carbon by substitution or by synthesis. They constitute what 
is known as the aliphatic ox fatty series, and are sharply dis- 
tinguished from another important and not less numerous 
class of organic compounds designated as the aromatic series. 
These latter are derived from benzene, C^H^, a hydrocarbon 
occurring in coal-tar, and they bear to this a relation similar 
to that which exists between methane and its derivatives. 

The term aromaiic is used because the first studied sub- 
stances of this series were obtained from aromatic resins and 
oils. It is now recognized that an aromatic smell or taste 
is not essential to these compounds, but the old name is still 
retained : we even speak of their " aromatic character" with 
reference to their chemical behavior. 

As a rule the aromatic compounds contain a larger propor- 
tion of carbon than the members of the fatty series ; never- 
theless, they generally behave like saturated compounds. 
They further differ from the aliphatic compounds in the 
facility with which they are modified by substitution, and 
the products of substitution exhibit many peculiarities which 
distinguish them from the marsh-gas derivatives. 



AROMATIC COMPOUNDS. 663 

Since tlie aromatic compounds are all derived from ben- 
zene, a clear conception of the constitution of this funda- 
mental body is of the utmost importance. It is thirty-five 
years since (1865) this problem began to engage the atten- 
tion of chemists, but in spite of the vast amount of work 
that has been done in this direction, it cannot be said that 
an entirely satisfactory and conclusive solution has been 
reached. We are chiefly indebted to Kekule and Baeyer for 
the theories which are now generally accepted as accounting 
for the peculiar character of the aromatic compounds. How- 
ever, before we can proceed to discuss these theories, it is 
necessary that we acquaint ourselves with the principal facts 
on which they are based. 

1. The hydrogen of benzene may be readily replaced by chlo- 
rine, bromine, etc., by which monochlorobenzene, monobromo- 
benzene, dichlorobenzene, etc., are obtained. 

C6H6 C^H^Cl C^H^Br 

Benzene. Monochlorobenzene. Monobromobenzene. 

Dichlorobenzene. Dibromobenzene. 

These chlorides and bromides are analogous to the corre- 
sponding compounds of the fatty series, but the chlorine or 
bromine is much more strongly combined with the benzene 
nucleus, and cannot be exchanged by double decomposition, as 
is the case with ethyl bromide and ethylene bromide, etc. 

2. By treatment with strong nitric acid, the hydrogen of 
benzene may be replaced by one or more groups (NO^), form- 
ing the following compounds : 

C6H6 C6H5-N02 C6H4<^Q2 

Benzene. Nitrobenzene. Dinitrobenzene.- 

3. The substitution of the group (NH^) for one atom of 
hydrogen produces phenylamine, or aniline ; that of two groups 
NH^ for two atoms of hydrogen yields phenylene-diamine. 

C6H6 C6H5-NH2 ^^^*<NH2 

Benzene, Phenylamine (aniline). Phenylene-diamine 

and its isomerides. 

4. The amines of benzene result from the reduction of the 
nitrobenzenes, but there are other products of the reduction of 
nitrobenzene. They are the a^o-derivatives, of which azoben- 
2ene, C^^H^^N^, discovered by Mitscherlich, is the type. They 



664 



ELEMENTS OF MODERN CHEMISTRY. 



contain two nitrogen atoms (N=N), so united that each pos- 
sesses one free atomicity which may be satisfied by a mona- 
tomic group such as C^H^. 

C6H5-N 

C12H10N2 = II 

C6H5-N 

By the action of nitrous acid on aromatic compounds con- 
taining the group NH^, peculiar explosive compounds are 
formed. They are the c?m;>;o-derivatives, and contain likewise 
the group N=N : one affinity, however, is satisfied by a mona- 
tomic aromatic group, while the other combines it with some 
other monatomic radical or element. Such is diazobenzene 
chloride. 

C6H5-N 

ci-isr 

Only a few diazo-compounds have been obtained in the 
fatty series, and these are distinguished from the aromatic 
diazo-compounds by their inability to form salts with the 
mineral acids. Azo-compounds appear to exist only in the 
aromatic series. 

5. Concentrated sulphuric acid eiFects the displacement 
of hydrogen in benzene by the group SO'H, sulphonic acids 
being formed. 

C6H6 C6H5S03H C6H*(S03H)2 

Benzene sulphonic acid. Benzene disulphonic acid. 



Sulphonic acids exist also in the fatty series, but direct 
sulphonation is a reaction characteristic of the aromatic 
compounds. 

6. The replacement of one or more atoms of hydrogen by 
the same number of hydroxyl groups converts benzene into 
compounds known as pheiioh. They correspond to the alco- 
hols of the saturated hydrocarbons, but, while the alcohols are 
perfectly neutral, the phenols have acid characters, although 
they are neutral to litmus. 

/OH 

C^HVOH 

\0H 

Phenol. Oxyphenol Dioxyphenol 

(resorcinol and isomerides). (phloroglucinol and 
isomerides.) 

7. If one or more atoms of hydrogen in benzene be replaced 
by as many methyl groups, CH^, the higher homologues qf 
benzene are obtained, 



C6H5.0H 



CeH^gH 



AROMATIC COMPOUNDS. 665 

C«H6 = C6H6 benzene. 

C'H8 = C6H5-CH3 toluene (methylbenzene). 

pTT3 

Q8JJ10 ^ C^H*<\pTT3 xylene and isomerides (dimethylbenzenes). 

C9JJ12 _ C^H^x— CH^ mesitylene and isomerides (trimetbylbenzenes). 
Ci2Hi8= C(CH3)6 hexamethylbenzene. 

One ethyl group can replace one atom of hydrogen in 
benzene, and ethylbenzene, isomeric with dimethylbenzene, 
results. 

C6H5-C2H5 C«H4<^g3 

Ethylbenzene. Dimethylbenzene. 

There are many instances of such isomerism, and they re- 
ceive the same interpretation. 

One atom of hydrogen in benzene may be replaced by a 
propyl group, C^H', and propyl benzene, which i^ isomeric 
with trimethylbenzene, is the result. 

One atom of hydrogen may be replaced by an ethyl group 
and another by a methyl group, and the new compound would 
be ethyl-methylbenzene, isomeric with propylbenzene and with 
trimethylbenzene. 

QJJ3 

C6H5-C3H7 C6H*<pS^ C6H3^CH3 

OH \^jj3 

Propylbenzene (cumene), [Ethyl-meythelbenzene. Trimethylbenzene. 

The alcoholic radicals, which are thus substituted for the 
hydrogen of benzene, constitute, according to the expression of 
Kekule, lateral chains, which are grafted, so to speak, on the 
benzene nucleus or principal chain. 

8. The aromatic acids, properly speaking, result from the 
substitution of one or more carboxyl groups, CO. OH = CO^H, 
for one or more hydrogen atoms in the benzene nucleus. 

C6H6 C6H5-C02H C6H*<^Q2H C6H3(C02H)3 C6(C02H)8 

Benzene. Benzoic acid. Phthalic acid Trimesic acid Mellitic acid. 

and isomerides. and isomerides. 

9. Isomerism of Constitution in Substituted Benzene De- 
rivatives. — In the homologues of benzene, the substitution of 
CI, Br, OH, NH^, CO^H, etc., for hydrogen, may take place 
either in the benzene nucleus or in the lateral chain : isomeric 
compounds are thus formed. 

a. By substitution of one atom of chlorine for an atom of 
hydrogen in toluene, two isomeric compounds, C^H^Cl, may be 
obtained. In one, the chlorine will be attached to the lateral 

56* 



666 ELEMENTS OF MODERN CHEMISTRY. 

chain ; in the other, it will be attached to the benzene nucleus, 
as is the group CH^ itself. 

C6H5-CH3 C6H5-CH2C1 C6H4<^^jj3 

Toluene. Benzyl chloride. Chlorotoluene. 

h. The phenols result from the substitution of OH for an 
atom of hydrogen in the nucleus. If this substitution take 
place in a lateral chain, an aromatic alcohol^ isomeric with the 
corresponding phenol, is obtained. 

C6H5-CH3 C6H5-CH2(OH) C6H4<^^3 

Toluene. Benzyl alcohol. Cresol. 

c. The substitution of a carboxyl group, CO^H, for an atom 
of hydrogen in the benzene nucleus of toluene, C^H^-CH^, pro- 
duces the aromatic acids, toluic acid, and its isomerides ; if, 
however, the carboxyl replace a hydrogen atom in the lateral 
chain, CH^, phenylace^ic (alpha-toluic) acid, isomeric with 
the preceding acids, results. 

C6H5-CH3 C6H4<^Q2H C6H5-CH2-C02H 

Toluene. Toluic acids. Phenylacetic acid. 

d. When two groups OH are substituted for two atoms of 
hydrogen in the principal chain, oxyphenols are formed. If 
this substitution takes place in both the benzene group and in 
the lateral chain, phenol alcohols result. 

C6H3^0H C6H4 < ^ 5^'^^ 

Orcinol. Saligeninol. 

e. The substitution of the group NH^ for one atom of 
hydrogen in the principal chain, on the one hand, and in the 
lateral chain, on the other, produces isomeric compounds. 

C6H5-CH(NH2) C6H*<^g3 

Benzylaniine. Toluidine. 

10. Isomerism of Position in Substituted Benzene Deriv- 
atives. — In addition to the preceding isomerisms, the lateral 
chains may be grafted at different points of the benzene nucleus 
by substitution for the different hydrogen atoms. Their posi- 
tions and their relative distances from each other are the causes 
of numerous isomerisms, called isomerisms of position, to dis- 
tinguish them from the isomerisms of constitution already 
explained. 

It is important to understand the principle of this isomei:-' 



AROMATIC COMPOUNDS. 667 

ism. Let us consider the most simple case, that in which 
two atoms of hydrogen are replaced by two other monatomic 
atoms or monatomic groups. Such compounds are the di- 
substituted derivatives of benzene, and experience has shown 
that there are three di-substituted derivatives of each kind. 

Thus there are three hydrocarbons containing two groups 
CH^, each substituted for one atom of hydrogen in benzene; 
three phenols, each containing two groups OH ; three acids, 
each containing one group CO'^H, and one group OH, substi- 
tuted each for one atom of hydrogen, and three acids, each 
containing two carboxyl groups substituted for two atoms of 
hydrogen. 

Theory of the Constitution of Benzene. — How then shall 
we account for the tenacity with which the six carbon atoms 
of benzene and of the benzene nucleus of its derivatives are 
held together? What explanation can be offered for the 
isomerisms of the substitution products peculiar to the aro- 
matic series? 

According to a theory propounded by Kekule in 1865, the 
6 atoms of carbon in benzene form a closed chain, each being 
bound to its neighbors, on one side by one, and on the other 
by two bonds of saturation. One atom of hydrogen is 
attached to each of these carbon atoms. 

H 

A 

H-C C-H 

U-b l>H 

Benzene.* 

Innumerable experiments have shown that the chemical value 
of each of the six hydrogen atoms of benzene is absolutely the 
same. If by the action of reagents one of these hydrogen atoms 
be replaced by another atom or group of atoms, it is a matter 
of indifference which of the hydrogen atoms is so replaced, 
the product is always identical. This fact indicates that the 

* In this formula, the connecting lines indicate the saturation of the 
atomicities; the double lines indicate the exchange of two atomicities 
between two neighboring atoms of carbon. 



668 



ELEMENTS OP MODERN CHEMISTRY. 



arrangement of the hydrogen atoms is perfectly symmetrical 
in relation to the carbon atoms around which they are 
grouped. In other words, the molecular constitution of ben- 
zene must be (CH)^ In consequence, each atom of carbon 
must be united to one atom of hydrogen, — a requirement met 
by Kekule's theory, — and each carbon atom must be sym- 
metrically related to the other carbon atoms with which it is 
combined. The latter condition is not perfectly satisfied by 
Kekule's theory, for a carbon atom would exchange a double 
aflfinity with its neighboring atom on one side, while with that 
on the other side it would exchange but a single atomicity. It 
would follow that the combination should be stronger on one 
side than on the other, and the molecule would not be sym- 
metrical. 

This difficulty disappears in the following formula proposed 
by Armstrong and by Baeyer, known as the centric formula : 



H-C 



H-C 




The 6 carbon atoms are arranged at the angles of a hexa- 
gon, as in the formula of Kekule, but instead of assuming a 
double linking of alternate pairs of carbon atoms, we con- 
ceive the fourth affinity of each carbon atom to be directed 
towards the centre, but without actually connecting any two 
carbon atoms with each other. While thus augmenting the 
stability of the molecule, the fourth affinity of each car- 
bon atom is rendered latent. Although this arrangement 
is the most satisfactory that has been proposed, it must be 
admitted that such a method of disposing of the valences 
is without analogy in the compounds we have thus far con- 
sidered. 

Isomerism of Position. — In the benzene molecule the posi- 
tion of each atom of hydrogen is of the same value. It 
will be convenient to represent the formula by a simple 



AROMATIC COMPOUNDS. 



669 



hexagon and to number tliese positions as in the following 
diagram : 

1 



According to Kekulg and Baeyer. 

Experiment has shown that if but a single atom of hydrogen 
in benzene be replaced by another monatomic atom or group, the 
resulting compound does not vary, and is incapable of isomerism. 
This is not, however, the case if two hydrogen atoms be re- 
placed, for theory then predicts, and experiment confirms, the 
existence of three isomeric compounds in each case. This 
isomerism results from the different positions of one of the 
substituted atoms or groups with relation to the other in their 
attachment to the benzene nucleus. Let X and Y be the two 
substituted monatomic atoms or groups, such as chlorine, hy- 
droxy 1, nitryl, etc., then the isomerism would be expressed as 
follows : 




CH 



CH 



cx 



CY 



CH 



'CH 



The position at 1 being always supposed to be occupied by 
one of the substituted groups, the compounds are named ortho 
if the other replacement be at 2 or 6, meta if it be at 3 or 5, 
and para if it be at 4. The relations of 2 and 6 to 1 are the 
same, as are also those of 3 and 5 to 1. 



ortho 



ortho 



meta 



para 



670 



ELEMENTS OF MODERN CHEMISTRY. 



In tlie preceding compounds formed by X and Y, these 
positions would be marked as follows : 



Ortho-derivative. 



C6H4< 



X(i) 



~Y(3) 
Meta-derivative. 



C6H4< 



X(i 



-Y(4) 
Para-derivative. 



The following examples will further explain this isomerism 
of position, of which we must study numerous cases. 



ORTHO-SERIES. 


META-SERIES. 


PARA-SERIES. 


X(, 


X(i) 

c 


X(, 


, ^ >, ,„ 


/ N 


y V, 


HC CY(2) 


HC CH 


HC CH 


HC CH 


HC CY(3) 


HC CH 


•\ / 


\ / 


\ / 


C 


C 


C 


H 


H 


Y(4) 


^ ^ <CH3(2) 


r6TT4^CH3(l) 
^^<CH3(3) 


C6m<^CH3(i) 
^ ^ <CH3(4) 


Ortlioxylene. 


Metaxylene. 


Paraxylene. 


r6TT4^CH3(l) 

^^<0H(2) 


r6TT4^CH3(l) 
^^<0H(3) 


c»H'<o°g;« 


Orthocresol. 


Metacresol. 


Paracresol. 


^ ^ <0H(2) 


C6H4^^H(1) 


C^H.<S«fl> 


Orthodiphenol, 


Metadiphenol. 


Paradipbenol. 


(pyrocatechin.) 


(resorcinol.) 


(hydroquinone.) 


^ ^ <C0.0H(2) 


r6m^0H(i) 

^ ^^ <C0.0H(3) 


^^ <C0.0H(4) 


Orthoxybenzoic acid. 


Metoxybenzoic acid. 


Paroxybenzoic acid. 


(salicylic.) 






^ ^ <^NH2(2) 


^^<NH2(3) 


p6m^NH2(l) 

^^<NH2(4) 


Orthopbenylene 


Metapbenylene 


Paraphenylene 


diamine. 


diamine. 


diamine. 


p6„4^NH2(l) 

^^<C0.0H(2) 


^ ^ \C0.0H(3) 


C6H4^^'H2(i) 
^^ <C0.0H(4) 


Orthoamidobenzoic acid. 


Metamidobenzoic acid. 


Paramidobeuzoic acid. 


^ ^^ <C0.0H(2) 


r6m^C0.0H(i) 
^^<C0.0H(3) 


^„,^CO.OH(i) 
^^<C0.0II(4) 


Phthalic acid. 


Isophthalic acid. 


Terephthalic acid. 



These indications will suffice to illustrate the class of isomer- 
ides under consideration. With the tri-substituted derivatives 
of benzene, theory foresees and experiment has demonstrated 
the existence of still more numerous isomerides, but we cannot 
dwell on them here. 

Two very important hydrocarbons are now considered as 
directly related to benzene. They are naphthalene, C'°H®, and 
anthracene, C^*H^». 



BENZENE. 671 

Naphthalene is formed by the union of two benzene nuclei, 
two atoms of carbon being common to each nucleus (Erlen- 
mejer). 

Anthracene results from the union of two benzene nuclei by 
the intermediation of two carbon atoms, which are themselves 
combined together, each by one atomicity, and each of which 
is combined with one atom of hydrogen (G-raebe). 

These ideas are indicated in the following graphic formulae, 
which express the reciprocal relations between the atoms of 
carbon and hydrogen, but not their real positions in space : 

H H H H H 

,C C C C H C 

HC CH HC C CH HC C-C-C CH 

HC CH HC, CH HC C-C-C CH 

H H H H n 

Benzene. Naphthalene. Anthracene. 

or their " centric" equivalents : 

CH CH OH 



CH 



CH HC 

cIh CTH CH 

Benzene Naphthalene 



BENZENE AND ITS DERIYATIYES. 
BENZENE, OR BENZOL. 

C6H6 

This important body was discovered in 1825 by Faraday. 
Mitscherlich obtained it by heating benzoic acid with an 
excess of lime. 

C^H^O^ = CO^ + C'W 

It is now obtained in large quantities from coal-tar by dis- 
tilling the latter body. The more volatile products contain 
the benzene, which is purified by fractional distillation. That 
which passes below 85° is principally benzene, and the latter 
crystallizes out when the liquid which passes between 80 and 



672 ELEMENTS OP MODERN CHEMISTRY. 

85° is cooled to — 5°. Tlie crystals are collected and sepa- 
rated by pressure from the adhering liquid. The product is 
benzene containing a very small proportion of a compound 
named thiophene (page 746), which may be removed by 
repeated agitation with strong sulphuric acid (Y. Meyer). 
Berthelot has made the direct synthesis of benzene by ex- 
posing acetylene to a temperature near redness. 

Acetylene. Benzene. 

Benzene is a colorless, strongly refracting liquid. At 0° it 
solidifies to crystals which melt at 5.5°. It boils at 80.5°. 
It is insoluble in water, but dissolves in alcohol and ether. It 
is inflammable, and burns with a bright, smoky flame. 

When benzene vapor is passed through a red-hot tube, di- 
phenyl^ C^^H^", is formed. 

2C«H« = C^HS-C^H*^ + H^ 

When heated to 275 or 280° for twenty-four hours with 
80 to 100 parts of concentrated hydriodic acid, benzene is 
converted into hexahydrohenzene^ Q^W^ (hexamethylene), 
iodine being set free. The formation of small amounts of 
hexane, C^H^*, has been observed in this reaction. 

CHLORINE AND BROMINE DERIVATIVES OF 
BENZENE. 

By the action of chlorine or bromine on benzene, two sorts 
of derivatives are obtained, — addition products and substi- 
tution compounds. 

Addition Compounds. — Two, four, or six atoms of chlorine 
may combine directly with benzene, forming the compounds 
Benzene dichloride, C^H^CP; 
Benzene tetrachloride, C^H^CF; 
Benzene hexachloride, C^H^CP. 
The last is easily formed by the action of an excess of chlo- 
rine on benzene exposed to direct sunlight. It crystallizes in 
brilliant plates. There is a corresponding hexabromide, formed 
in the same manner. Boiling potassium hydrate removes the 
elements of three molecules of hydrochloric acid from benzene 
hexachloride, converting it into trichlorobenzene. 
C«H^C1« = 3HC1 -]- C^H'CP 
Substitution Compounds. — These compounds are nuraer- 



CHLORINE AND BROMINE DERIVATIVES OF BENZENE. 673 

OTIS, and present interesting examples of isomerism. Only tlie 
mono-, penta-, and hexa-derivatives have no isomerides. 

MonocMorohenzene or phenyl chloride, C^H^Cl, is obtained 
by passing chlorine through benzene in the presence of a small 
quantity of iodine. It is also formed by the action of phos- 
phorus pentachloride on phenol : hence the name phenyl chlo- 
ride. 

C^H^OH + PCP = HCl + POCP + C^H^Cl 

Chlorobenzene is a colorless, strongly refracting liquid, 
having a pleasant odor, and boiling at 132°. It is readily 
prepared by heating diazobenzene chloride (page 687) with 
cuprous chloride (Sandmeyer). 

C«H^-N=N-C1 = C^H^Cl + N=^ 

Dichlorohenzene, C^H*CP. — There are three isomerides : — 

Ortho-dichlorobenzene, C^H*<n}Q, liquid, boiling at 179°. 

Meta-dichlorobenzene, C^H*<p|>3^ liquid, boiling at 172°. 

Para-dichlorobenzene, C^H^^pjW, fusible at 56°, and boil- 
ing at 173°. 

Among the other chloro-derivatives we will mention only 
hexachlorobenzene, C^CP, which is formed not only by the 
complete chlorination of benzene, but also when vapor of 
chloroform or of carbon tetrachloride, CCP, is passed through 
a red-hot tube. It is a crystallizable solid, fusible at 222°, 
and boiling at 332°. 

Monohromohenzene, C^H^Br, may be made by mixing ben- 
zene and bromine in the proportion of one molecule of the 
first to two atoms of the second, adding some thin iron wire, 
and heating for several hours over a small flame. The prod- 
uct is washed with caustic potash and distilled. A more 
convenient method is to warm diazobenzene bromide with 
cuprous bromide. Monobromobenzene boils at 157°. When 
heated with sodium, it yields to the latter its bromine, and a 

hydrocarbon C^^H^** =1 , called diphenyl, is obtained. 

Dibromo-henzenes, C^H'^Br^ — There are three isomerides-. 
The para-derivative, C*H*<^ \J, is readily formed by the 
2d ss 67 



674 ELEMENTS OP MODERN CHEMISTRY. 

action of an excess of bromine on benzene. It crystallizes 
in beautiful prisms, fusible at 89°. It boils at 218°. 

Iodine and fluorine derivatives of benzene are also known. 



NITRO-DERIVATIVES OF BENZENE. 

Nitrobenzene, C^H^(NO^). — If benzene be poured in small 
portions into a mixture of strong nitric and sulphuric acids, 
and water be added to the mixture, an oily, yellow liquid 
separates, constituting nitrobenzene. 

C«H« + HNO' = WO + C«H5(NO0 

It is benzene in which one hydrogen atom is replaced by the 
group (NOO'- 

Nitrobenzene is a yellowish liquid, having a strong odor of 
bitter almonds. It boils at 205°, and solidifies at 3°. It is 
employed in perfumery under the name essence of Mirhane. 

By the action of reducing agents, such as hydrogen sulphide, 
ammonium sulphide, tin and hydrochloric acid, or iron-filings 
and acetic acid, nitrobenzene is converted into aniline or phe- 
nylamine. 

C«HS(NO^) + 3H2 = 2W0 + C«H5(NH0 

Nitrobenzene. Aniline. 

Dmitrobenzenes, C^H*(NO^)l—The three isomerides are 
formed when benzene is treated with a large excess of a mixture 
of nitric and sulphuric acids. The nitro-compounds separate 
on the addition of water, and are purified by crystallization in 
alcohol. Metadinitrobenzene separates first, crystalHzing in long 
colorless needles, fusible at 89.9°. Reducing agents convert it 
successively into nitrophenylamine and phenylene-diamine. 

CeH<NOX') c«H*<NO'(') C«H<NffC) 

Metadinitrobenzene. Metanitrophenylamine. Metaphenylenediamine. 



AZO-DEBIYATIVES OF BENZENE. 

Besides aniline, there are other products of the reduction of 
nitrobenzene, and they are of great importance, for they have 
become types of numerous analogous compounds. The first 
was described in 1834, by Mitscherlich, under the name of 
azobenzide ; it is now called azobenzene. 



AZO-DERIVATIVES OP BENZENE. 675 

Azobenzene, C^^H'^N^, is obtained by the action of sodium 
amalgam on an alcoholic solution of nitrobenzene. 

Azobenzene forms large red crystals, fusible at 66.5°. It 
boils at 293°. It is only slightly soluble in water, but dis- 
solves readily in alcohol and ether. 

Azoxybenzene, C^^H^°NO. — This compound, which is a 
product of the incomplete reduction of nitrobenzene, was dis- 
covered by Zinin. It is formed by boiling an alcoholic solution 
of potassium hydrate with nitrobenzene. Under these conditions 
the alcohol is oxidized by the oxygen of the group NO^ 

2C«H5.N02 + SH^ = 3H^0 + 1 >0 

Azoxybenzene. 

Azoxybenzene crystallizes in long needles, soluble in alcohol 
and ether, insoluble in water. It melts at 36°, and is decom- 
posed when distilled. If heated with iron filings, it becomes 
converted into azobenzene. 

Hydr azobenzene, C^^H^^N^. — Alkaline reducing agents, 
such as zinc dust and sodium hydroxide, and ammonium sul- 
phide, in presence of alcohol, convert azobenzene into hy- 
drazobenzene. 

C6H5-I^ C6H5-NH 

II + H2 = I 

C6H5-N C6H6-NH 

Azobenzene. Hydrazobenzene. 

The latter body crystallizes in tables, fusible at 131°, almost 
insoluble in water but soluble in alcohol and ether.. When 
submitted to dry distillation, it breaks up into azobenzene and 
aniline. 

I! = II + 2C«H5.NH2 

Hydrazobenzene. Azobenzene. Aniline. 

Acids convert hydrazobenzene into a basic isomeride, ben- 
zidine, from which a number of valuable dye-stuffs (azo-dyes) 
are derived. 

Hydrazobenzene. Benzidine. 



676 ELEMENTS OP MODERN CHEMISTRY. 

Hydrazobenzene may be considered as derived from dia- 

mide, I , by replacement of two hydrogen atoms by phenyl 

groups. The aromatic hydrazines proper are the unsymmet- 
rical derivatives resulting from the substitution of one or 
two aromatic radicals for hydrogen in one Nff group. 

Phenylliydrazine. Di-phenylhydrazine. 

Phenylhydrazine is obtained by reducing diazobenzene 
chloride with sodium sulphite or stannous chloride. 

C«mN=NCl + 2W = C^H^-NH.NH^HCl 

It is a colorless oil, solidifying upon cooling in tabular 
crystals which melt at 17.5°. It boils at 241° with partial 
decomposition. The density at 23° is 1.097. Phenylhydra- 
zine is sparingly soluble in water, but readily in alcohol and 
ether. 

It acts as a powerful base, forming salts with the acids. 
Its property to react with aldehydes and ketones to form 
hydrazones has made it a most important reagent for the 
detection and isolation of those bodies, especially the sugars. 
Antipyrine and a number of dye-stuffs are derived from it. 

BENZENESULPHONIC ACID. 
C6H5-S02.0H 

Aromatic compounds are readily acted upon by concen- 
trated or fuming sulphuric acid, the sulphonic group (SO'^.OHy 
replacing one or several atoms of hydrogen. 

Thus, henzenesulphonic acid is formed in the following re- 
action : 

C6H6 + S02<^^ = H20 + C6H5.S02.0H 

It is prepared by heating for a long time a mixture of 
equal parts of benzene and concentrated sulphuric acid. The 
liquid is then diluted with a large quantity of water, and 
neutralized with barium carbonate. The concentrated solu- 
tion then yields a barium salt, Ba(C'H^SO0' + H^O, which 
crystallizes in pearly plates. From this salt the acid can be 
liberated by the careful addition of sulphuric acid. It crys- 



PHENOL, OR CARBOLIC ACID. 677 

tallizes in small plates, soluble in water and alcoliol. When 
fused with an excess of potassium hydroxide, it yields phenol. 
Benzene Sulphone, or Sulphobenzide, (C«H5)^S0l— The 
hydroxyl group in benzenesulphonic acid may be replaced by 
a phenyl group, and the compound so formed is called sulpho- 
benzide. It may be obtained by heatiEg phenylsulphuric acid 
with phosphoric anhydride to 150° in sealed tubes, treating the 
product of the reaction with a dilute alkaline hydrate, and crys- 
tallizing the residue in alcohol. It crystallizes from water in 
silky needles, and from benzene in large rhombic prisms. It 
melts at 128°. 

CYANOBENZENE. 

(phenyl cyanide, benzonitrile.) 

C6H5.cn 

This body is formed in various reactions, particularly in the 
destructive distillation of hippuric acid, and by the dehydration 
of benzamide by phosphoric anhydride. 

C^H^-CO.NH^ — H^O = C^H^-CN 

Benzamide. Benzonitrile. 

It is a colorless oil, which boils at 191°. When heated with 
the alkalies, it yields benzoic acid and ammonia. 

C^H^-CN -I- 2H20 = C^H^-CO^H + NH^ 

Benzonitrile. Benzoic acid. 

PHENOL, OR CARBOLIC ACID. 

C6H5.0H 

This body bears the same relation to benzene that wood- 
spirit does jbo marsh gas : it is hydroxy-benzene. 

CH* CH3.0H 

Methane. Methyl hydroxide. 

C6H6 C6H5.0H 

Benzene. Phenol. 

It was discovered in coal-tar by Runge, who named it car- 
bolic acid. Laurent demonstrated that it plays the part of an 
alcohol. Indeed, it presents points of resemblance with the 
monohydric alcohols, but it differs from them by its acid char- 
acter, on account of which it is sometimes called plienic acid. 

Preparation. — Large quantities of phenol are obtained from 
coal-tar, from which it is separated by distillation. That part 

57* 



678 ELEMENTS OF MODERN CHEMISTRY. 

which passes between 150° and 200° is collected apart and 
mixed with a saturated solution of potassium or sodium hy- 
droxide to which solid caustic alkali is added. A crystalline 
phenate of potassium or sodium is formed ; it is dissolved in 
boiling water, the insoluble oil which floats is separated, and 
the alkaline solution is neutralized with hydrochloric acid. 
The phenol separates ; it is washed with a small quantity of 
water, dehydrated with calcium chloride, and rectified. The 
distilled product is cooled to — 10°, and the crystals which are 
deposited are allowed to drain out of contact with the air. 

Phenol may be made artificially from benzene by a process 
which is applicable to the preparation of all the phenols. It 
consists in treating benzene with fuming or even ordinary 
sulphuric acid. Benzenesulphonic acid is formed ; this is 
diluted with water to separate the excess of hydrocarbon, 
and the solution is neutralized with chalk ; calcium phenyl- 
sulphonate, which is soluble, and sulphate, which is insoluble, 
are formed. The calcium benzenesulphonate is converted into 
sodium salt by double decomposition with sodium carbonate, 
and after evaporation and desiccation the product is fused 
in a silver crucible with an excess of potassium hydroxide. 
The mass is exhausted with water, and the alkaline solution 
is decomposed by hydrochloric acid. The phenol separates 
and is dried and purified by distillation (Dusart, Wurtz, 
Kekule). 

The decomposition of sodium or potassium benzenesul- 
phonate is expressed in the following equation : 

C^H^SO^K + KOH = C«H^OH -\- K'^SO^ 

Potassium benzenesulphonate. Phenol. Potassium sulphite. 

There is another very simple synthesis of phenol. In pres- 
ence of aluminium chloride, benzene absorbs oxygen directly 
and phenol is formed. 

C«H« + = C^H^O 

This reaction is one of the most unexpected and most in- 
teresting applications of a general method of synthesis discov- 
ered by Friedel and Crafts (see page 698). 

Phenol is also formed by the dry distillation of the oxy- 
benzoic acids (page 709). 

Oxybenzoic acid. Phenol. 



PHENOL, OR CARBOLIC ACID. 679 

Properties of Phenol. — Phenol is a solid, crystallizing in 
long, colorless needles, having at 0° a density of 1.084, It 
fuses at 42°, and boils at 183°. Its odor is peculiar and 
characteristic, its taste acrid and burning. It is poisonous and 
antiseptic. It is very soluble in alcohol, ether, and acetic acid, 
and dissolves in 15 parts of water at 20°. Its solution is 
colored dark violet by ferric salts, and bromine water forms, even 
in very dilute solutions, a yellow precipitate of tribromophenol. 
A. pine shaving moistened with hydrochloric acid assumes a 
blue color when dipped in phenol and exposed to the air. 

Although phenol is neutral to litmus-paper, it forms definite 
combinations with the alkalies. When it is mixed with a very 
concentrated solution of potassium hydrate, a crystalline mass 
is obtained which constitutes potassium phenate, C^H^.OK. 

The same compound is formed, with disengagement of 
hydrogen, by the action of potassium on phenol. 

The solubility of phenol in the alkaline hydrates is applied in 
the separation of this body from the neutral oils which accom- 
pany it. The property is common to the phenols, and indicates 
the slightly acid character of the class. 

Phosphorus perchloride converts phenol into phenyl chloride, 
identical with monochlorobenzene. 
C^H^OH + PCP = C^H^Cl + POCP -f- HCl 

Phenol. Phenyl chloride. 

The hydrogen of the radical C^H^ in phenol can be readily 
replaced by chlorine, bromine, or groups such as NO^ NO, NH*, 
etc. The compounds so formed may sometimes be obtained 
directly, as the nitro-phenols, — sometimes by indirect processes. 

In the presence of sodium, phenol directly combines with 
carbon dioxide, forming salicylic acid (page 709). 

C^H^OH -I- CO^ + Na^ = C«H^<^^-^^^^ + H=^0 

Sodium-salicylate of sodium. 

The following remarkable reaction of phenol was first noticed 
by Reimer and Tiemann. When it is heated with chloroform 
and an excess of sodium hydrate, in the proportion of one 
molecule each of phenol and chloroform and four molecules of 
alkali, it is converted into salicylaldehyde. 

C'H^ONa+SNaOH+CHCP = C^H50^Na+3NaCl+2H20 

Sodium phenate. Sodium salicylite. 

The compound CH^O^Na is the sodium compound of sali- 
cylaldehyde, into which it is converted by hydrochloric acid. 



680 ELEMENTS OF MODERN CHEMISTRY. 



ETHERS OF PHENOL. 

Phenyl Oxide, (C«H^)^0.— This body is formed, together 
with other products, by the dry distillation of copper benzoate. 
It crystallizes in long needles, fusible at 28°. It boils at 246°. 
It is very soluble in alcohol and in water. It cannot be 
reduced by either zinc or hydriodic acid. 

Methylphenyl Oxide, or Anisol, nTTs >0. — Anisol was 

first obtained by distilling anisic acid (page 712) with barium 
oxide or lime. 

Anisic acid. Anisol. 

It may be prepared more readily by synthesis in the reaction 
of methyl iodide on potassium phenate. 

C^HIOK + CH^I = KI + C^H^OCH* 

It is a colorless liquid, having an ethereal odor. Its density 
at 15° is 0.991 ; it is insoluble in water, and boils at 152°. 

Ethylphenyl Oxide, or Phenetol, r)2TT5>0, may be ob 

tained by a process analogous to the last method indicated for 
preparing anisol. It is an aromatic liquid, boiling at 172°. 
Phenylsulphuric Acid is analogous to ethylsulphuric acid. 

Ethylsulphuric acid. Phenylsulphuric acid. 

The acid is not known in the free state. Its potassium salt 
is formed when potassium phenate is heated with an aqueous 
solution of potassium pyrosulphate, K^S^O^ It exists in the 
urine of herbivorous animals. If phenol be ingested, it appears 
in the urine as potassium phenylsulphate (Baumann). 

SUBSTITUTED DERIVATIVES OF PHENOL. 

Among the numerous compounds derived from phenol by 
the substitution of various elements or groups for the hydrogen 
of the group C^H^, we can only describe a few of the nitro- 
and sulphonic compounds. 

Mononitrophenols, C^H*<qjj.— There are three iso- 
meric mononitrophenols. Two of them, the ortho- and the 



SUBSTITUTED DERIVATIVES OF PHENOL. 681 

para-, are formed by the action of dilute nitric acid on phenol. 
The meta-derivative is obtained by indirect processes. 

C«mOH + NO^OH :== C«H*<^^' + H^O 

Orthonitroplienol crystallizes in large yellow prisms, slightly 
soluble in water, fusible at 45°, and boiling at 214°. It is 
readily carried over with vapor of water, and may so be sepa- 
rated from the para-isomeride. 

Metanitrophenol is in yellow crystals, fusible at 96°, and 
quite soluble in water. It does not distil with vapor of water. 

ParanitropJienol deposits from its boiling aqueous solution 
in long colorless needles, fusible at 114°. They redden on 
exposure to the air. 

Nascent hydrogen (tin and hydrochloric acid) converts the 
mononitrophenols into amido-phenols. 

/N.OH 
Nitrosophenol, or duinonemonoxime, C^HV i . — 

By the action of potassium nitrite and acetic acid, phenol is 
converted into nitrosophenol. 

This compound is also formed by the action of hydroxyla- 
mine upon quinone (see page 696), thus : 

/O /N.OH 

Nitrosophenol crystallizes from hot aqueous solutions in fine, 
colorless needles. It dissolves in water, alcohol, and ether, 
forming pale-green solutions. It becomes brown on exposure 
to the air, and explodes when heated to 110-120°. . 

Trinitrophenol, or Picric Acid, C^H^NO^/.OH.— When 
phenol is boiled with concentrated nitric acid, it is converted 
into trinitrophenol. 

C^H^OH 4- 3HN0^ = SH^O + C^H\NO^)^OH 

This body has long been known, and is generally called 
picric acid. It deposits from boiling water in lemon-yellow, 
crystalline plates, only slightly soluble in 'cold water. Its taste 
is very bitter. It has acid properties, the three groups NO' 
seeming to increase the basic nature of the hydrogen atom of 
the group OH. With bases it forms crystallizable salts which 
detonate with violence when heated. 



682 



ELEMENTS OF MODERN CHEMISTRY. 



Potassium picrate, C^H^(NO^)^OK, crystallizes in long, 
yellow needles, soluble in 14 parts of boiling water and in 
250 parts at 15°. It explodes violently when heated or 
struck. 

Picramic Acid. — When a current of hydrogen sulphide is 
passed through an alcoholic solution of picric acid saturated 
with ammonia, sulphur separates and the picric acid is con- 
verted into picramic acid (A. Girard). 

C6H2(N02)3.0H -f 3H2S = 2H20 + S^ + C6H2(N02)2(NH-^)OH 

Picric acid. Picramic acid. 

The hydrogen sulphide partially reduces the picric acid, and 
one of the three groups (NO"^) is thus converted into a group 
(NH^). Picramic acid is dinitro-amido-phenol, that is, phenol 
in which two atoms of hydrogen are replaced by two groups 
(NO^), and a third atom of hydrogen by the group NH^. 

When acetic acid is added to a hot aqueous solution of the 
ammonium salt of picramic acid, the picramic acid is deposited 
in fine red needles, which melt at 170°. 

Phenol-sulphonic Acids. — These bodies bear the same re- 
lation to phenol that benzenesulphonic acid bears to benzene. 



C6H6 

Benzene. 

C6H5-S02.0H 
Benzenesulphonic acid. 



C6H5.0H 
Phenol. 

Phenol-sulphonic acids. 

^^^^<(S02.0H)2 
Phenol-disulphonic acids. 






-The three 



Phenol-sulphonic Acids, 

isomeric phenol-sulphonic acids are known. The ortho- and 
para-compounds are formed when phenol is dissolved in con- 
centrated sulphuric acid. The first is formed in large quantity 
in the cold, and is readily converted into the para-derivative by 
heat. The excess of sulphuric acid is separated by neutralizing 
with chalk, removing the calcium sulphate by filtration, and 
decomposing the solution of the calcium salts with potassium 
carbonate. When evaporated, the solution first deposits potas- 
sium para-phenolsulphonate in hexagonal plates, and the 
ortho-phenolsulphonate afterwards crystallizes out in needles, 
containing two molecules of water. The latter salt is very 
soluble in water; if heated with an excess of potassium 
hydrate it is converted into pyrocatechin (page 693). 



ANILINE, AMIDOBENZENE, OR PHENYLAMINE. 683 

C«H*<^^ OK + ^^^^ ^ ^'^^' + ^'^ + ^'^*<oi 

Potassium phenolsulpbonate Potassium compound 

of potassium, of pyrocatechin. 

The ortlio acid is used as an antiseptic (aseptoV). 

MetapTienolsulphonic acid has also been isolated. It crys- 
tallizes in j5ne needles, containing two molecules of water. 
When heated with an excess of potassium hydrate it yields 
resorcinol (page 693). 



ANILINE, AMIDOBENZENE, OR PHENYLAMINE. 

C6H7N = C6H5.NH2 

Aniline was discovered by Unverdorben among the products 
of the distillation of indigo, and was extracted from coal-tar by 
Runge. It is now prepared artificially by a process discovered 
by Zinin. This process consists in converting benzene into 
nitrobenzene, and subjecting the latter to the action of re- 
ducing agents (see nitrobenzene). 

Iron and hydrochloric acid are advantageously used to 
accomplish this reduction on a large scale ; in the laboratory 
tin is generally substituted for the iron. 

Aniline is a colorless, mobile, highly-refracting liquid, having 
a peculiar, unpleasant smell, and an acrid, burning taste. Its 
density at 0° is 1.036. It boils at 184.8°. When exposed to 
the air, it becomes brown and is eventually resinified. When 
pure, it may be solidified by cold, and then fuses at — 8°. 

Aniline is almost insoluble in water, but mixes in all pro- 
portions with alcohol, ether, and the fatty and volatile oils. 

It does not restore the blue color to reddened litmus-paper, 
but nevertheless possesses the character of a base, for it 
forms well-defined salts with the acids. 

Reactions. — 1. If a nitrate and sulphuric acid be added to 
aniline, a red color is produced. 

2. If a few drops of aniline be poured into an excess of sul- 
phuric acid, and a small quantity of potassium dichromate be 
added, a magnificent blue color is developed, which changes to 
violet on the addition of water. 

3. A solution of calcium hypochlorite (chloride of lime) 
added to aniline produces a beautiful violet tint. 

4. When a solution of an aniline salt is heated with cupric 
chlorate, an intense black color is developed (Ch. Lauth). 



684 



ELEMENTS OF MODERN CHEMISTRY. 



These reactions are applied in the arts in the preparation 
of coloring matters of wonderful brilliancy. Among the 
more important of these are rosaniline or magenta^ and para- 
rosaniline.^ which will be described farther on. 

5. When aniline is added to a mixture of chloroform and 
alcoholic potash, and heat is applied, the penetrating and 
characteristic smell of phenylcarbylamine is noticed. 

Salts of Aniline. — These are obtained by saturating aniline 
by the acids. 

Aniline hydrochloride^ C^H^N.HCl, forms colorless needles, 
which are fusible, and can be distilled without alteration ; they 
are very soluble in water and in alcohol. Platinic chloride pre- 
cipitates from the solution fine yellow needles of a chloro-plati-- 
nate, (C^H^N.HCiyPtCl*. 

Aniline oxalate, (C^IFN)^C''^H^O*, crystallizes from water in 
hard, thick prisms. When heated, it loses tbe elements of 
water, and is converted into oxanilide. 

Aniline oxalate. Oxanilide. 



ANILIDES. 

By the action of heat, tbe aniline salts lose the elements 
of water, and form compounds which are analogous to the 
acid amides, and which Gerhardt named anilides. When ani- 
line acetate is heated, it is converted into acetanilide, which 
is no other than acetamide in which an atom of hydrogen is 
replaced by a phenyl group, (C^H^). 



<^^<l^. 




Oxamide. 


Phenyl oxamide (oxanilide). 


C2IP0.NH2 


C2H30.NH(C6H5) 


Acetamide. 


Phenylacetamide (acetanilide). 



Acetanilide is readily obtained by boiling equi-molecular 
quantities of aniline and glacial acetic acid. It may be 
purified by crystallization in boiling water. 

It melts at 114°, is readily soluble in hot water and in 
alcohol. Under the name of antifehrin, it is used in medicine 
as an antipyretic. 



DIPHENTLAMINE, 685 

ALKYL DERIVATIVES OF ANILINE. 

The alcoholic radicals may be substituted for one or both of 
the hydrogen atoms related to the nitrogen in aniline, thus 
forming secondary and tertiary amines. Among these we will 
only consider methyl-aniline and dimethyl-aniline, which are 
obtained in the arts by heating to 220° a mixture of aniline, 
aniline hydrochloride, and wood-spirit. The product contains 
the hydrochlorides of the methyl-anilines. 

Methyl- Aniline, C^H^-NH(CH^), is a colorless liquid, which 
gradually becomes brown. Its density at 15° is 0.976, and it 
boils at 190-191°. By the action of nitrous acid on methyl- 
aniline, or, better, by the addition of methyl-aniline hydrochlo- 
ride to a solution of potassium nitrite, a thick oil, nitrosomethyl- 
aniline, is obtained. 

n^ch^ + no.oh = h^o + n^ch^ 

\h Xno 

It is methylaniline in which the hydrogen atom of the group 
NH is replaced by the nitrosyl group, NO. 

All of the secondary aromatic amines undergo analogous reac- 
tions. 

Dimethyl-aniline, C^H^-N(CH^)^, is an oily liquid, boiling 
at 192°, and solidifying at 5°. Its density is 0.945. When it 
is submitted to the action of nitrous acid, the phenyl group 
is attacked. 

.Cm^ /C^H^NO 

N^CH^ + NO.OH = H^O + N^Cff 
Ncff \CH^ 

Dimethyl-aniline. Nitrosodimetliylaniline. 

Nitrosodimethylaniline, produced by this reaction, crystallizes 
in green plates. It may be obtained by treating dimethyl-ani- 
line hydrochloride with ethyl nitrite or amyl nitrite. 

A number of valuable dyes, malachite green, for example, 
are derived from dimethyl-aniline. 

DIPHENYLAMINE. 

This body is derived from ammonia by the substitution of 
two phenyl groups for two atoms of hydrogen. It is formed 
in various reactions, of which the most interesting was discov- 

58 



686 



ELEMENTS OF MODERN CHEMISTRY. 



ered by Girard and de Laire. It consists in heating aniline 
hydrochloride to 256° with aniline. Ammonia is disengaged, 
and diphenylamine hydrochloride is formed. 



C6H5) C6H5) 

H [ N.HCl + H ^ N 

hJ hJ 



C6H5 [ N + NH4C1 

hJ 



Free diphenylamine forms crystals fusible at 54°. It boils 
at 310°. It is insoluble in water, but dissolves in alcohol, 
ether, benzene, and petroleum. Its odor recalls that of oil 
of rose. Its basic character is not very pronounced, for its 
salts are readily decomposed by water. 

When heated with a mixture of oxalic and sulphuric acids, 
it yields a splendid blue color, soluble in water, and known 
as diphenylamine blue (Girard and de Laire). 

When a trace of nitric acid is added to diphenylamine 
dissolved in strong sulphuric acid, an intense blue color is 
developed. This is a delicate test for nitric acid. 



DIAZOBENZENE COMPOUNDS. 



Nitrous acid exerts an energetic action upon aniline and 
the analogous bases ; it is indicated here because it presents 
a great generality and gives rise to remarkable bodies, dis- 
covered by p. G-riess, and known as diazo-compounds. 

When a current of nitrous vapors — generated by the action 
of nitric acid upon arsenic trioxide — is passed into a saturated 
solution of an aniline salt, such as the nitrate, crystals of 
diazobenzene nitrate are deposited. 

C^H'N.HNO^ + HNO^ = 2H^0 + C^H^N^.NO' 

Auiline nitrate. Diazobenzene nitrate. 

This body is formed by the substitution of one atom of nitro- 
gen for three atoms of hydrogen in aniline nitrate. 

C6H5-NH2.HN03 aniline nitrate. 
C6H5-N=N-(N0') diazobenzene nitrate. 

It forms long, colorless prisms, very soluble in water, slightly 
soluble in alcohol, and insoluble in ether. It explodes violently 
by heat or by percussion. 

Besides this nitrate, there are other compounds of diazoben- 
zene. They all contain the diatomic group N=:N, combined 



DIAZOBENZENE COMPOUNDS. 687 

on one hand with phenyl, and on the other with chlorine, 
bromine, or an oxidized group. The following formulae will 
explain their constitutions : 

C6H5-]Sr=N.Cl diazobenzene chloride. 
C6H5_N=N.Br diazobenzene bromide. 
C6n5-N'=N.N03 diazobenzene nitrate. 
C6H5-N=N.SO*H diazobenzene sulphate. 

These compounds present several interesting reactions. 

1. When heated with water, they disengage nitrogen, and 
are converted into phenols. 

C^H^NINO' _|_ H^O = C^H^.OH + N^ -}- HNO^ 

2. When they are boiled with absolute alcohol, they are re- 
duced to hydrocarbons, nitrogen being disengaged and the 
alcohol being transformed into aldehyde. 

Diazobenzene sulphate. Aldehyde. Benzene. 

3. When warmed with cuprous salts, diazo-compounds give 
off nitrogen gas and are converted into substitution products 
of benzene. 

C«H5-N:=N.Br = C^H^Br + N'' 

It is thus possible to replace the NH^ group in aromatic 
compounds by the halogens or cyanogen. This is known as 
Sandmei/er' s reaction. 

4. With auric and platinic chlorides, diazobenzene chloride 
forms double salts. When the platino- chloride is submitted 
to dry distillation, it yields chlorobenzene. 

(C«H5.N^Cl)'PtCl* = 2C'WGl + N^ + 2CP + Pt 

5. Diazobenzene bromide can fix two atoms of bromine, 
and the bromide so formed yields, on dry distillation, nitro- 
gen, bromine, and bromobenzene. 

C^H^N^Br^ = C^H^Br + Br^ + N^ 

A very convenient method of diazotizing aromatic amines 
consists in acidifying a mixture of their salts and sodium 
nitrite (Y. Meyer and Ambuhl). It is unnecessary to isolate 
the compounds from the resulting solution in order to bring 
about the above reactions, which support the view already 
presented of the constitution of diazo-compounds. 

Diazoamidobenzene. — When aniline is added to an aque- 
ous solution of diazobenzene nitrate or chloride, a diazo- 



688 ELEMENTS OF MODERN CHEMISTRY. 

compound is obtained whicli is more complex than tlie pre- 
ceding and is called diazoamidohenzene. 
C^H^N^CNOO + NHlC«H5=rC«H5-N2-NH.C«H5 + HNO« 

Diazobenzene nitrate. Aniline, Diazoamidobenzene. 

The same body is formed when a current of nitrogen tri- 
oxide is passed into a cooled alcoholic solution of aniline. It 
forms brilliant, golden-yellow scales, fusible at 91°. It ex- 
plodes at a higher temperature. 

If an alcoholic solution of diazoamidobenzene be left to 
itself, or, better, if it be warmed with a small proportion of 
aniline hydrochloride, it undergoes a curious transformation, 
first noticed by Kekule. The diazo-compound is converted 
into an azo-derivative, amidazobenzene. 

Diazoamidobenzene. Amidazobenzene. 

This change shows the difference existing between the azo- 
derivatives described on page 675, and the diazo-compounds. 
Both contain the diatomic group N^N, but in the former com- 
pounds it is related to two aromatic groups, while in the latter 
it links together an aromatic group, and a monatomic atom or 
group. This may be understood from the following formulas : 

Azo-derivatives. Diazo-derivatives. 

Azobenzene. DiazobenzenecMoride. 

Amidazobenzene. Diazoamidobenzene. 

The salts of diazobenzene react not only with aniline and the 
other primary and secondary aromatic amines, yielding diazo- 
amidobenzene and its analogues ; they undergo analogous re- 
actions with other aromatic compounds, such as the phenols, 
naphthols, tertiary aromatic amines, metaphenylene-diamine, 
etc. These reactions invariably form azo-compounds, of 
which a large number are manufactured and used as dye- 
stuffs. An example is the action of diazobenzene nitrate on 
phenol, and on its sulpho-derivative, metaphenolsulphonic 
acid (page 683). 

C6H5-N2-N03 + C6H5.0H = C6H5-N2-C6H4.0H + HN03 
Diazobenzenenitrate. Phenol. Azobenzene-phenol. 

C«H6-N2-N03 + C6H*<g^3jj = C6H5-N2-C6H3<^5h + ^^^' 
Metaphenolsulphonic Azobenzene-pheoolsulphonic 
acid. acid. 



ROSANILINE AND ITS DERIVATIVES. 689 

The last compound is the sulphonic acid of azobenzene- 
phenol, and is one of that class of dye-stuffs known as 
tropaeolines. 

These compounds have acquired great importance from 
their applications in dyeing. That they are numerous may 
be understood if it be considered that all aromatic compounds 
containing the group NH^ may be converted into diazo- and 
azo-compounds by the methods which have just been indi- 
cated. 

ROSANILINE AND ITS DERIVATIVES. 

C20H21N3O 

The magnificent red coloring matter known as magenta is 
the chloride of rosaniline : it is obtained by oxidizing a mix- 
ture of aniline and ortho- and para-toluidine by means of 
nitrobenzene or arsenic acid. A mixture of equal molecular 
proportions of the three bases, with enough hydrochloric acid 
to saturate two-thirds, and nitrobenzene, is heated to 190°, 
while small quantities of iron are introduced. With the aid 
of a current of steam the excess of nitrobenzene, as well as 
the unchanged part of the bases, is expelled from the product, 
and the residue is dissolved in water. Upon addition of salt 
and hydrochloric acid, rosaniline chloride separates out ; by 
recrystallization it is obtained in magnificent crystals which 
present a green reflection, like the scales of cantharides, and 
dissolve in alcohol with a rich purple color. 

The formation of rosaniline is represented by the following 
equation : 

C^H^N + 2C^H«N -f 0^ == C^^H^^N^O + 2H20 

Aniline. Toluidine. Eosaniline. 

More recently rosaniline has been manufactured syntheti- 
cally by heating paranitrobenzoic aldehyde, (CHO)C^H*-NO'^, 
with aniline and sulphuric acid. 

Properties of Rosaniline. — The methods of preparation 
just indicated furnish the salts of rosaniline, such as the 
chloride, which is the rich red coloring matter known as 
magenta or fuchsine. The free base is obtained by treating 
a hot, saturated solution of the chloride with an excess of 
soda. The rosaniline separates as an almost colorless, crys- 
talline precipitate. It is a triacid base which requires three 
molecules of hydrochloric acid for its saturation. 
U 58* 



690 ELEMENTS OE MODERN CHEMISTRY. 

The monochloride of rosaniline, C^H^^WCl (magenta), 
forms dark-colored, rhombic tables, having a splendid green 
reflection. It is but slightly soluble in water, but dissolves 
readily in alcohol, forming an intense purple solution. 

The trihydrochloride, C'°HiW.3HCl, forms yellow-brown 
needles which lose hydrochloric acid when heated or when 
dissolved in water. 

Rosaniline and its salts present two important reactions : 

1. When a salt of rosaniline is treated with reducing agents, 
such as nascent hydrogen (zinc and hydrochloric acid), the 
base fixes two atoms of hydrogen and is converted into leuco- 
rosaniline^ C^^H^'^N^, a white powder slightly soluble in water. 

2. By the action of nitrogen trioxide, rosaniline is converted 
into a diazo-derivative which yields rosolic acid when boiled 
with water (pages 687 and 692) and diphenyltolyl methane, 

CH\ X6TT4_pTT35 when heated with alcohol. 

Commercial magenta is not a pure salt of rosaniline. Be- 
sides certain isomerides of this base, it contains considerable 
quantities of pararosaniline, C^^H^WO, of which rosaniline 
is the next higher homologue. Our knowledge of these bases 
and their chemical composition is chiefly due to Hofmann, 
but it is to the researches of E. and 0. Fischer that we are 
indebted for the true explanation of their constitution. 

These chemists have shown that pararosaniline and rosani- 
line must be regarded as derivatives of triphenylmethane, 

CH(C«H5)^ and diphenyl-tolylmethane, CH^^?,^')g3. 

Upon treatment with strong nitric acid, these hydrocarbons 
yield substitution products in which the three hydrogen atoms 
occupying the para-positions to the CH group are replaced 
by the nitro-group, and the nitro-compounds are converted 
by reduction into the corresponding amido-derivatives. The 
latter are leuco-pararosaniline and leuco-rosaniline ; upon oxi- 
dation, they give para-rosaniline and rosaniline. 

The constitution of these bases is expressed by the formulae 
/C«H*.NH2 /C6H4.NH2 

C(OH)^C6H4.NH2 C(0H)^C8H*.NH2 

\C6H4.NH2 \C6H3(CH3).NH2 

Pararosaniline or triamido- Rosaniline or triamido-diphenyl- 

triphenylcarbinol. tolylcarbinol. 

By subjecting the corresponding leucanilines to the action 
of nitrous anhydride, and reducing the diazo-compounds thus 



COLORING MATTERS FROM ROSANILINE. 691 

formed by alcoliol, the same chemists also obtained the hydro- 
carbons C'W and C^^H'^ 

Coloring Matters derived from Rosaniline.— When rosan- 
iline is heated with ethyl iodide, three atoms of hydrogen are 
replaced by three ethyl groups, and this triethyl-rosaniline 
yields with the acids a magnificent violet color, known as Hof- 
mann's violet. 

Triphenyl-rosaniline, in which three atoms of hydrogen are 
replaced by three phenyl groups, C^H^, is formed when rosani- 
line is heated with an excess of aniline. This reaction, in 
which ammonia is disengaged, was discovered by Grirard and 
de Laire. 

Q20H2i]S[3o -I- SC^H^NH^ = Q'^m'XQmyWO + 3NH' 

Kosaniline. Aniline. Triphenyl-rosaniline. 

The hydrochloride of triphenyl-rosaniline is of a magnifi- 
cent blue color, and is known as aniline blue or Lyons blue 
(Ch. Girard and de Laire). The following formulae show 
the interesting relations which exist between rosaniline and 
its ethyl and phenyl derivatives : 

C2ojj2i^3Q C^offXC'H^yN^O C'°H^XC'H5)3N'0 

Eosaniline. Triethyl-rosaniline. Triphenyl-rosaniline. 

(Base of Hofmann's violet.) (Base of Lyons blue.) 

We may mention among the derivatives of rosaniline Paris 
violet and the aniline greens, particularly the beautiful color- 
ing matter known as night-green, because it retains its rich 
green tint in artificial light. 

Paris violet, first manufactured by Poirrier, is a splen- 
did color, produced by the oxidation of methylaniline or 
dimethylaniline. 

C6H5) C6H5) 

CH3 y N CH3 I N 

hJ CH3j 

Methylaniline. Dimethylaniline. 

Ch. Lauth realizes this oxidation, or rather dehydrogena- 
tion, by heating methylaniline with cupric chloride. The 
reaction is complex, and, according to Hofmann and Martins, 
gives rise to trimethyl-rosaniline. 

When heated with methyl chloride, the base of Paris violet 
fixes two molecules of that compound, forming a combination 
of trimethyl-rosaniline and methyl chloride. This combination 
constitutes night-green. 

Dichloromethylate of trimethyl-rosaniline 
(night-green). 



692 ELEMENTS OF MODERN CHEMISTRY. 



ROSOLIC ACIDS. 

To the rosanilines which have been described correspond 
derivatives containing hydroxyl, and which have been named 
rosolic acids. They contain two hydroxyl groups, substituted 
for two groups NH^ of the rosanilines, and an atom of oxygen 
which replaces the remaining NH^ group and the group OH. 

C^^HiXNH^)lOH C^^H^^A^^)' 

Pararosaniliue. Aurin. 

Kosaniline. Rosolic acid. 

AURIN AND ROSOLIC ACID. 

When IJ part of phenol is heated with 1 part of oxalic 
acid and 2 parts of sulphuric acid, it is converted into a color- 
ing-matter, which was first described under the name rosolic 
acid, or coralline-yellow. The same body or analogous bodies 
may be obtained by means of the rosanilines (see farther on). 
Indeed, it has been recognized that there are several homolo- 
gous bodies having the properties and the constitution of roso- 
lic acid. 

Rosolic acid made from pure phenol contains C^^H^^O^, and 
is called aurin (Dale and Schorlemmer). It occurs in very 
brilliant, red, triclinic prisms having a blue or green reflec- 
tion. Rosolic acid proper is a methyl derivative of aurin. 

Aurin was formerly used in dyeing. When it is heated to 
180° with an alcoholic solution of ammonia, it is converted 
into a bright-red coloring matter, noticed by Persoz, and 
employed in dyeing under the name coralline-red. 

DIOXYBENZENES. 

C6H^(OH)2 
Three isomeric bodies having the composition C^H*0^ = 

OTT 
C*II*<^TT are known ; they are derived from benzene by the 

substitution of two hydroxyl groups for two atoms of hydro- 
gen. These three bodies are pyrocatechin, resorcinol, and 
hydroquinone. 



DIOXYBENZENES. 693 

Pyrocatechin, or Catechol, ^^H*<Qjj>2y is so named 

because it was first obtained by the destructive distillation 
of catecbu. It is also produced by tbe distillation of gum 
kino and various tannins which produce a green color with 
ferric salts. It is generally prepared by conducting hydro- 
iodic acid gas into guaiacol, C®H*(OH)(OCH^), heated to 
195°. Pyrocatechin is a solid body, very soluble in water 
and alcohol, very slightly soluble in ether ; it crystallizes from 
its aqueous solution in rectangular prisms, belonging to the 
orthorhombic system. It melts at 104°, and sublimes below 
that temperature in brilliant, colorless plates. It boils be- 
tween 240 and 245°. Its odor is strong and excites sneezing. 
It has the character of an acid, like phenol itself. It dis- 
solves in the alkalies and in the alkaline carbonates. When 
exposed to the air, these solutions become colored, first green, 
then brown and black. An aqueous solution of pyrocatechin 
produces a deep-green color with ferric chloride, which 
changes to dark-red on the addition of an alkali. This re- 
action characterizes the ortho-dihydric phenols. 

Resorcinol, C'^H*<qtt/3m which is the homologue of orci- 

nol, C'H^O', is formed when certain gums, such as galbanum, 
asafoetida, gum ammoniac, sagapenum, etc., are fused with 
potassium hydrate (Hlasiwetz and Barth). It is manufac- 
tured on a large scale by fusing benzene meta-disulphonic 
acid with caustic potash. 

C6H*<sQ3i + 2K0H = C6H*<QH + 2K2S03 

The fused mass is dissolved in water, supersaturated with 
sulphuric acid, filtered, and the filtered solution shaken with 
ether, which dissolves the resorcinol. After having driven 
off the ether on a water-bath, a residue is obtained which is 
distilled: the resorcinol sublimes and condenses in radiated 
crystals. 

Resorcinol is also obtained from many other di-substituted 
benzenes — ortho- and para- as well as meta-derivatives — by 
fusion with alkaline hydroxides. 

Resorcinol forms colorless, prismatic or tabular crystals. 
It melts at 110°, and boils at 276°. It is very soluble in 
water, alcohol, and ether, but insoluble in chloroform. With 
ferric chloride its aqueous solution gives a violet color. 



694 ELEMENTS Or MODERN CHEMISTRY. 

Like other meta-dihydric phenols it yields d. fluorescein with 
phthalic anhydride. When a mixture of resorcinol and the 
anhydride is strongly heated, and the residual mass is dis- 
solved in dilute alkali, a brownish solution exhibiting green 
fluorescence results. 

Hydroquinone, C*^H*<^jjy.~This body is formed when 

para-iodophenol, C^H*<y .4. ^ ^, is fused with potassium hy- 
droxide, or more readily by the action of reducing agents, such 
as sulphur dioxide, on quinone. 

C^H^O^ _|_ H2 == C^H'^O^ 

W(3hler, who discovered it, found it also among the products 
of the dry distillation of quinic acid. 

Hydroquinone crystallizes in beautiful, transparent, and col- 
orless, hexagonal prisms. It has no odor ; its taste is sweet- 
ish. It dissolves in 17 parts of water at 15°, and is very 
soluble in alcohol and ether. It melts at 169°, and solidifies 
at 165°. When gently heated, it sublimes in brilliant plates, 
like those of sublimed benzoic acid. It partially decomposes 
when abruptly heated. When its vapor is passed through a 
tube heated to dull redness, it breaks up into quinone and 
hydrogen. Various oxidizing agents, such as chlorine, ferric 
chloride, nitric acid, and potassium dichromate, transform it 
into a substance which deposits in magnificent green needles 
having a metallic reflection. It is quinhy drone, C^^H^^O*, a 
combination of quinone and hydroquinone. 

Hydroquinone is used as a developer in photography. 

QUINONE. 
C6H402 

This remarkable body, discovered by Woskresensky, is a 
product of the oxidation of quinic acid, which exists in cin- 
chona bark. It may be obtained by distilling that acid with a 
mixture of manganese dioxide and sulphuric acid. The mass 
swells up and disengages vapors of quinone, which condense in 
the receiver in brilliant, golden-yellow needles. They are pressed 
between folds of filter-paper and purified by resublimation. 

It is also formed when various para disubstituted benzenes, 
such as phenylene-diamine, amidophenol, phenolsulphonic 



QUINONE. 695 

acid, etc., are treated with oxidizing agents. The best 
method of preparation consists in adding a concentrated 
solution of sodium dichromate (3 parts) to a well-cooled 
mixture of aniline (1 part), water (25 parts), and sulphuric 
acid (8 parts). The dark-colored liquid is extracted with 
ether, the latter evaporated, and the product crystallized 
from petroleum ether. 

Quinone crystallizes in long, brilliant, transparent needles 
of a golden-yellow color. It is very soluble in cold water, 
and more soluble in alcohol and ether. It melts at 115.7° 
to a yellow liquid. Quinone sublimes at ordinary tempera- 
tures, emitting pungent vapors which excite tears. 

Chlorine converts it into a trichloro-derivative, C^HCPO*, 
crystallizable in small, yellow prisms, fusible at 164-166°. 

When treated with a mixture of potassium chlorate and 
hydrochloric acid, quinone is converted into tetrachloroquinone, 
C^C1*0^ better known as chloranile. This name was given by 
Erdmann, who first obtained this body by the action of chlorine 
on indigo, of which the Portuguese name is anil. The same 
body is formed by the action of a mixture of potassium chlorate 
and hydrochloric acid on a great number of aromatic com- 
pounds, such as phenol, picric acid, salicylic acid, salicin, isatine, 
etc. Tetrachloroquinone forms pale-yellow scales, having a 
pearly, metallic lustre. When gently heated, it sublimes with- 
out fusing, and leaves no residue. It is insoluble in water and 
almost insoluble in cold alcohol, but dissolves in boiling alcohol 
and separates on cooling in golden-yellow scales. 

Constitution of Quinone and Hydroquinone. — According 
to Grraebe, these bodies are allied to benzene, from which the first 
is derived by the substitution of two atoms of oxygen for two 
atoms of hydrogen ; but as the two atoms of oxygen represent 
four atomicities, of which two only are employed in replacing 
H^ in benzene, the other two serve to bind together the two 
atoms of oxygen. The couple (0' -0")" can indeed play the 
part of a diatomic group. In the formation of hydroquinone, 
these atoms of oxygen separate from each other and each fixes 
one atom of hydrogen, so that two hydroxyl groups are formed 
and substituted each for one atom of hydrogen in benzene. The 
following formulae express these relations : 

C6H6 C6H4< ? C6H*<0H 

benzene. Quinone, Jlydroquinone, 



696 



ELEMENTS OF MODERN CHEMISTRY. 



In certain respects, however, quinone resembles the di- 
ketones. The observation that upon treatment with hy- 

/O 
droxylamine both a monoxime, C^H*< i , and a dioxime, 

/N.OH 

C^H*<^ I , are produced, is perhaps best explained by the 

following centric formula, which also satisfactorily exposes 
the relation between quinone and hydroquinone. 

OH 






OH 



PHLOROaLUCINOL. 

C6H603 = C6H3(OH)3 

Phloroglucinol and its isomeride pyrogallol are trioxyben- 
zenes ; they represent benzene in which three atoms of hy- 
drogen are replaced by three hydroxyl groups. The relations 
between phloroglucinol, dioxybenzene, and phenol are the 
same as those between glycerol, propylene glycol, and propyl 
alcohol. 



C3H7,OH 

Propyl alcohol. 



C6H5.0H 



C3H6{^H 
Propylglycol. 
C6H* ^ ^^ 



roH 

C3H5 \ OH 

(oh 

Glycerol. 

roH 
emu OH 

(OH 

Phloroglucinol. 



lOH 
Phenol, Dioxybenzene. 

Phloroglucinol was discovered by Hlasiwetz, who obtained 
it by heating phloretin (page 659) with a very concentrated 
solution of potash. It is also formed in many other reac- 
tions, especially when resorcinol, gum-kino, gamboge, and 
dragon's-blood are fused with potassium hydroxide. 

Phloroglucinol crystallizes in hard, rhombic prisms, having 
a very sweet taste. It is quite soluble in water, alcohol, and 
^ther. Its aqueous solution is neutral, and produces a deep- 



TOLUENE AND ITS DERIVATIVES. 697 

violet color with ferric chloride. Its ethereal solution, evap- 
orated upon a microscope-slide, deposits prisms in tangled, 
tree-like forms which are very characteristic. 

The crystals deposited from ether are anhydrous, while 
those formed in water contain two molecules of water of 
crystallization, which they lose at 100°. The dry crystals 
melt at 220°. 

The chemical character of phloroglucinol is very curious. 
While in many respects it behaves like a trihydric phenol, — 
it forms salts with the alkalies and a triacetate with acetyl 
chloride, — it is also capable of reacting like a triketone: 
with hydroxylamine, for example, it yields the trioxime 
C^H^(N-OH)l Bodies which react as if they belonged to 
two distinct chemical classes are said to be tautomeric. 

Phenols containing more than three hydroxyl groups have 
been obtained. The potassium compound of hexoxybenzene, 
C^(OK)^, constitutes the explosive potassium carbonyl (page 



TOLUENE AND ITS DEEIYATIYES. 
TOLUENE. 

Toluene is a homologue of benzene. It was discovered 
in 1837 by Pelletier and Walter ; H. Deville obtained it by 
distilling balsam of Tolu ; hence its name. It exists in coal- 
tar, and is separated from that body, like benzene, by frac- 
tional distillation. It is methyl-henzene, or pTienylmethane, 
and has been obtained by synthesis by heating a mixture of 
methyl iodide and monobromobenzene with sodium (Fittig 
and Tollens). 

C^ffBr + CH^I 4- 2Na = Nal + NaBr + C^H^-CH' 

Monobromobenzene. Methyl-phenyl. 

A method of synthesis of toluene, which by the generality 
of its applications is one of the most fecund in chemistry, is 
due to Friedel and Crafts. It consists in the reaction of 
methyl chloride on benzene in presence of aluminium chlo- 
ride. Toluene is formed, and hydrochloric acid is disengaged. 
2b 59 



698 ELEMENTS OF MODERN CHEMISTRY. 

It is probable that tbe aluminium chloride first acts on the 
benzene, disengaging hydrochloric acid and forming a phenyl 
derivative of aluminium chloride, which derivative is con- 
tinually formed and continually decomposed by the methyl 
chloride. The cycle of reactions would then be represented 
by the following two equations : 

G'W -f APCP = APCP(C'H^) + HCl 
APCP(C^H5) -I- CH^Cl = CRXCW) + APCP 

We may add that the toluene thus formed may react with an 
excess of methyl chloride, forming hydrochloric acid and dime- 
thyl benzene (xylene), which in its turn may react upon an ex- 
cess of methyl chloride. It is thus seen that the methylation 
of benzene does not stop with the first substitution compound, 
and that the nature of the products formed depends upon the 
proportions of the bodies which react. Friedel and Crafts 
thus succeeded in introducing six methyl groups into ben- 
zene, and made the synthesis of hexamethylbenzene. 

C«H« + eCH^Cl = 6HC1 + C«(CH3)« 

Hexamethylbenzene. 

Properties of Toluene. — Toluene is a colorless liquid, insol- 
uble in water. Its density at 0° is 0.882, and it boils at 111°. 

When it is boiled with dilute nitric acid or a solution of 
chromic acid, it is transformed into benzoic acid. 

C«IP-CH' + 0^ = C«H^-CO.OH + H^O 

Toluene. Benzoic acid. 

As is indicated, the methyl group is attacked and converted 
into carboxyl, CO.OHo 

SUBSTITUTION PRODUCTS OF TOLUENE. 

These compounds are numerous, and present various isomer- 
isms, of which we will consider the principles. 

C^H^ 

When chlorine acts upon toluene, i , one or more atoms 

CH^ 
of hydrogen may be removed and replaced by as many atoms 
of chlorine. The most simple of the products thus formed is 
the compound C^H^Cl, which results from the substitution of 
one atom of chlorine for one atom of hydrogen in toluene, CH^. 
But this substitution may take place in the benzene nucleus 



SUBSTITUTION PRODUCTS OF TOLUENE. 699 

CH^, or in the group CH^, and two isomeric bodies are tlius 
formed, monochlorotoluene and benzyl chloride. 

C6H*C1 C6H5 

CH3 CH2C1 

Monochlorotoluene. Benzyl chloride. 

QJJ3 

Monochlorotoluene, C^H*<^p, , is a di-substituted derivative 

of benzene ; it may consequently exist in three isomeric mod- 
ifications, as has already been explained (page 670). 

It is thus seen that there are four different bodies derived 
from toluene by the substitution of one atom of chlorine for 
one of hydrogen, namely, benzyl chloride and three monochlo- 
rotoluenes. 

The following; table includes a number of toluene derivatives ; 



CSH^Cl 


C6H4(NH2) 


C6H*(0H) 




C6H4(OH) C6H4(0H) 


CH3 


CH3 


CH3 




CHO CO.OH 


Monochlo- 


Toluidine. 


Cresol. 




Salicyl Salicylic acid. 


rotoluene. 








aldehyde. 


C6H5 


C6H5 


C6H5 


C6H5 


C6H5 


CH2C1 


CH2(NH2) 


CH2.0H 


CHO 


CO.OH 


Benzyl 


Benzyla- 


Benzyl 


Benz- 


Benzoic acid. 


chloride. 


mine. 


alcohol. 


aldehyde. 





Among these compounds, those placed in the same vertical 
line present isomerisms easily understood from the formulae, 
which express their constitutions and show the atomic group- 
ings. 

The bodies in the first horizontal series constitute di-sub- 
stituted compounds of benzene. 

C6H4^CH3 ^6p4^CH3 g ^^CHO pexT.^CO.OH 

^ ^ <^NH2 ^ ^ <-0H ^^ <0H ^ -^ <0H 

Toluidines. Cresols. Salicyl aldehyde. Salicylic acid. 

Hence they may exist in three different isomeric modifica- 
tions, and consequently there are four isomerides of each of 
these derivatives of toluene, excepting salicylic acid, just as 
for monochlorotoluene. 

Chloro-Berivatives of Toluene. — The momchhrotoluenes 
are formed by the action of chlorine on cold toluene. Ortho- 
and metachlorotoluene are liquids boiling between 156 and 
157°. Parachlorotoluene boils at 160.5°, and below 0° solidi- 
fies to a mass which melts at 6.5°- 

Benzyl chloride, C^H^-CH^Cl, is formed when chlorine ia 
passed into boiling toluene. 



700 ELEMENTS OF MODERN CHEMISTRY. 

Benzalchloride, C^HICHCP, and BenzotricMoride, 
C^H^CCP, are also formed by the direct action of chlorine 
on boiling toluene. The former boils at 206° and the latter 
at 213°. The beautiful green dyestuff, malachite- or aldehyde- 
green, is formed by the action of zinc chloride on a heated 
mixture of benzotrichloride and dimethylaniline. 

Nitrotoluenes. — Monohydrated nitric acid attacks toluene 
and converts it into nitrotoluenes, C^H^(NO^), and dinitro- 
toluenes, according to the duration of the reaction. There 

riTT3 

are three nitrotoluenes, C^H*<^^2- 

Orthonifrotoluene, fusible at 10.5° to a yellow liquid, which 
boils at 218°. 

Metanitrofoluene, crystals, fusible at 16°. Boils at 230- 
231°. 

Paranitrotoluene, almost colorless prisms, fusible at 54°, 
and boiling at 230°. 

Binitrotoluene, C^H^(NO^)^CH^, is formed when toluene is 
treated with a mixture of nitric and sulphuric acids. Long 
needles, almost colorless, fusible at 70.5°. An isomeride is 
known, fusible at 48°. 



CRESOLS. 

C^HSO := C6H*<™' 

There are three cresols, two solid and one liquid. They 
may be formed artificially by treating toluene with sulphuric 
acid, according to the process indicated on page 678, but in 
this reaction several isomeric sulphonic acids are formed, and 
when decomposed by caustic potash they yield different cresols. 
The different isomers are best obtained from the correspond- 
ing toluidines by means of the diazo-reaction (p. 687). 

The cresol discovered by Fairlie, and extracted from wood- 
tar by Duclos, is a colorless liquid, having an odor like that 
of phenol. It boils at 190°, and appears to be a mixture. 

Orihocresol is a crystalline mass, fusible at 31°, and boiling 
at 185-186°. 

Metacresol is a liquid, boiling at 201°. 

Paracresol forms colorless prisms, fusible at 36°. It boils 
at 198° (A. Wurtz). 



ORCINOL — TOLUIDINES. 701 



OECINOL. 



C7H802 = C^Hs/™^. 



This body is an oxycresol. It was discovered by Robiquet 
in 1829, and is obtained, at the same time as erythritol, by 
decomposing erytbrin by slaked lime at 150°. 

The orcinol is deposited first in beautiful crystals from tbe 
solution wbich contains botb substances, and it is purified by 
recrystallization. It forms colorless, hexagonal prisms, con- 
taining one molecule of water of crystallization. It melts at 
58°, losing its water, and the anhydrous orcinol boils at 290°. 

The crystals of orcinol become rose-colored in the air. 
When ammonia is added to their aqueous solution and the 
liquid is exposed to the air, it absorbs oxygen and assumes 
first a violet color and afterwards a brown. A nitrogenized 
body is formed which is known as orcein, and constitutes the 
coloring principle of the archil of commerce. 

The synthesis of orcinol has been made by the action of 
fused potassium hydroxide on the sulphonic acid of mono- 
chlorotoluene (cresyl chloride, C^H*C1.CH^). The chlorine 
and the group SO^H of this compound are thus replaced by 
two groups OH (Vogt and Henninger). 

rci fOH 

C6H3 { S03K -h 2K0H = SO^Rz + KCl + G^W \ OH 
i CH3 { CH3 

Potassium chlorocresyl- Orcinol. 

sulphonate. 

TOLUIDINES. 

C^H^N = C6H4(NH2)-CH3 

Paratoluidme. — Solid toluidine, which is paratoluidine, was 
discovered by Hofmann and Muspratt in 1848. They obtained 
it by the reduction of paranitrotoluene by ammonium hydro- 
sulphide. This reduction may also be accomplished by iron 
and acetic acid, or by tin and hydrochloric acid. 

en^NO^) -f 3H^ ^ C^H^(NH^) + 2^0 

Nitrotoluene. Toluidine. 

An interesting method of formation of paratoluidine was dis- 
covered by Hofmann and Martins. When methylaniline hydro- 
chloride is heated to 350° under pressure, paratoluidine hydro- 



702 



ELEMENTS OF MODERN CHEMISTRY. 



chloride is formed. The methyl group which is united to the 
nitrogen of the former base is then transposed and exchanged 
for an atom of hydrogen of the phenyl group. 





^C6H4-CH3 


N^H 


H 


^H 


iethylaniline. 


Toluidine. 



Paratoluidine is a solid heavier than water. It crystallizes 
from its dilute alcoholic solution in large plates. It melts at 
45°, and boils at 198°. It is almost insoluble in water, but 
very soluble in alcohol and in etber. 

Toluidine exists nearly always in commercial aniline. It is 
important and necessary for the preparation of certain aniline 
colors. 

Orthotoluidine was discovered by Eosenstiehl in commercial 
toluidine, which is a mixture of para- and orthotoluidine. It is 
formed by the reduction of orthonitrotoluene by nascent hy- 
drogen. It is liquid and does not solidify at — 20°. It boils 
at 199.5°. 

Metatoluidine. — A colorless liquid, boiling at 19*7°. Density 
at 25°, 0.998. 

BENZYL ALCOHOL. 

C^H^O = C^HS-CH^.OH 

Benzyl alcohol is readily prepared by the action of potas- 
sium hydroxide upon benzaldehyde ; one molecule of the 
aldehyde is oxidized to benzoic acid, while another is reduced 
to benzyl alcohol. 

2C«H^CH0 + KOH = C^H^COOK + C^H^CHIOH 

Benzaldehyde. Potassium benzoate. Benzyl alcohol. 

It is also formed by boiling benzyl chloride with soda solu- 
tion, 

C^Hs.CH^Cl + H^O = C'H^CH^OH + HCl, 

and by the action of nascent hydrogen upon benzaldehyde, 

C^H^CHO -f H^ :^ C^H^Cff.OH 

Benzyl alcohol is a colorless, oily liquid, having a faint 
but agreeable odor. It boils at 207°. Density at 0°, 1.0628. 

When heated with nitric acid, it is converted into benz- 
aldehyde (oil of bitter almonds). 

CWO -f = H^O + C^H^O 



BENZ ALDEHYDE. 703 

Chromic acid oxidizes it to benzoic acid. 

C^H^O + 0^ = H^O + C^H^O^ 

The relations between benzyl alcohol, benzaldehyde, and 
benzoic acid are the same as those between alcohol, aldehyde, 
and acetic acid. 

CH3-CH2.0H alcohol. C6H5-CH2.0H benzyl alcohol. 

CH3-CH0 aldehyde. C6H5-CHO benzaldehyde. 

CH3-C02H acetic acid. C6H5-C02H benzoic acid. 

Benzyl Compounds. — Benzyl chloride^ C^H^Cl = C^H^- 

CH^Cl, is formed, as has already been remarked, when chlorine 
is passed into boiling toluene. It is also formed by the action 
of hydrochloric acid on benzyl alcohol by the aid of heat. It 
is a colorless liquid having an irritating odor. It boils at 
176°. 

Benzylamine, C^H^-CHINHI— This body is formed by the 
action of nascent hydrogen on benzonitrile (phenyl cyanide), 
which thus fixes four atoms of hydrogen. It is also formed 
in small quantity, together with dibenzylamine and tribenzyl- 
amine, when benzyl chloride is heated with alcoholic ammonia. 
It is a limpid liquid, boiling at 185°, and miscible with water, 
alcohol, and ether. Density, 0.99 at 14°. 

Trihenzylamine, (C^HICII^)^N. — This is formed in abun- 
dance by the action of a hot alcoholic solution of ammonia on 
benzyl chloride. It crystallizes in beautiful, colorless needles 
or plates, fusible at 91°. It is insoluble in water, slightly 
soluble in cold alcohol, very soluble in hot alcohol and in ether. 



BENZALDEHYDE. 

C^H60 = C6H5-CHO 

This body, formerly called benzoyl hydride, exists in the 
essential oil of bitter almonds, mixed with hydrocyanic acid, 
both substances being formed by the action of emulsin and 
water on amygdalin (page 658). 

Grimaux and Lauth have obtained it by oxidizing benzyl 
chloride by boiling with nitrate of lead or of copper. 

C«H5-Cff CI + ^ HCl + C«ff-CHO 



704 ELEMENTS OF MODERN CHEMISTRY. 

Benzaldehyde is a colorless, strongly-refracting liquid, 
having a pleasant odor and a pungent, aromatic taste. It 
boils at 179.5°. 

When its vapor is passed through a porcelain tube filled 
with pumice-stone and heated to redness, benzaldehyde 
breaks up into benzene and carbon monoxide. 

c^H«o = CO + cm' 

When exposed to air and light, it absorbs oxygen, and is 
converted into benzoic acid. 

C'H^O + = C^HW 

Benzoic acid. 

Like the aldehydes of the fatty series, benzaldehyde re- 
duces ammoniacal solutions of silver ; it combines with 
sodium-acid sulphite, and yields characteristic compounds 
with hydroxylamine and phenylhydrazine. 

Benzaldehyde reacts with diamide (hydrazine) readily 
with elimination of water (Curtius). 

N^H* + 2C«H^CH0 = N^C^ff .CH7 + 2H20 

The resulting henzalazine melts at 93°. 

Nascent hydrogen, produced by the action of water on 
sodium amalgam, transforms benzaldehyde into benzyl alco- 
hol (Friedel). 

C^H^O + H^ = C'H^OH 

Chlorine converts it into benzoyl chloride. 

C^H^O.H -f CP = HCl 4- C^H^O.Cl 

Benzaldehyde. Benzoyl chloride. 

Benzaldehyde readily undergoes condensation with other 
carbon compounds, and is therefore much used for syn- 
thetical purposes. 

Benzoin, C«H^-CH(OH)-CO-C^H^— When crude oil of 
bitter atmonds containing hydrocyanic acid is mixed with 
alcoholic caustic potash, or when the pure oil is mixed 
with an alcoholic solution of potassium cyanide, the benz- 
aldehyde is polymerized and converted into a solid body, 
which is benzoin^ C'^H'^0'^ The latter crystallizes in brill- 
iant, colorless prisms, fusible at 133-134°. It is but slightly 
soluble in water and cold alcohol, very soluble in boiling 
alcohol. Oxidation converts it into benzil. 



BENZOIC ACID. 705 

Benzil, or Dibenzoyl, C^H^-CO-CO-C^H^ is the aromatic 
diketone which corresponds to diacetyl. It forms yellow 
hexagonal prisms, melting at 95°, and soluble in alcohol and 
ether. Benzil combines directly with hydrocyanic acid and 
with hydroxylamine. Both the monoxime and the dioxime 
exist in several stereoisomeric forms. 

Benzoyl Chloride, C^H^-COCl.— This body is formed by 
the action of phosphorus pentachloride on benzoic acid or 
a dry benzoate. It is a colorless, highly-refractive liquid, 
having a peculiar, irritating odor. It boils at 199°. Water 
decomposes it into benzoic and hydrochloric acids. 

C^ffO.Cl + H^O = C^H^O.OH + HCl 

Ammonia converts it into benzamide. 

C'H^OCl + NH^ = C^H^O.NH^ + HCl 



Benzoyl chloride may exchange its chlorine for other ele- 
ments. When it is distilled with potassium iodide, potassium 
chloride and benzoyl iodide are formed. Liebig and Wohler, 
who discovered these important reactions, prepared in the 
same manner, by double decomposition, benzoyl sulphide and 
benzoyl cyanide. These experiments are celebrated ; they 
were the starting-point of the benzoyl theory^ which marked 
an important progress in the development of the theory of 
radicals. The following formulae indicate the principal benzoyl 
combinations : 

(C7H50)2 dibenzoyl (benzil). 

C^H^O.H benzoyl hydride (oil of bitter almonds). 

C'HSO.Cl benzoyl chloride. 

CHSO.I benzoyl iodide. 

(C7H50)2S benzoyl sulphide. 

(C'^H50)20 benzoyl oxide (benzoic anhydride). 

C^HoO.OH benzoyl hydroxide (benzoic acid). 

Cm50.NH2 benzamide. 



BENZOIC ACID. 

CTH602 = C6H5-C02H 

Preparation. — This acid may be obtained from gum benzoin. 
That resin is placed in a flat dish over the top of which a sheet 
of tissue-paper, or light filter-paper is glued (Fig. 133), This 



706 



ELEMENTS OP MODERN CHEMISTRY. 




Fig. 133. 



diaphragm forms the base of a paper cone which is then placed 

over the dish, which is moderately heated on a sand-bath for 

several hours. At the 

end of that time, the 

whole is allowed to 

cool, and the benzoic 

acid is found in light, 

brilliant, crystalline 

flakes on the sides of 

the cone, and on the 

diaphragm. 

The benzoin resin 
may also be powdered 
and digested with milk 
of lime for twenty- 
four hours ; it is then 
heated to ebullition 
and filtered. Hydro- 
chloric acid precipi- 
tates benzoic acid from the filtered liquid, which contains cal- 
cium benzoate. 

Benzoic acid is also prepared by boiling the urine of horses 
and cows with hydrochloric acid. The hippuric acid which 
these urines contain is thus decomposed into benzoic acid 
and glycocoll. The benzoic acid crystallizes on cooling, and 
is purified by sublimation. 

On a large scale benzoic acid is now generally obtained 
by oxidizing toluene or benzyl chloride with nitric acid. 

Properties. — Benzoic acid crystallizes in needles, or in thin, 
brilliant plates. It has an aromatic odor, and a slightly acid 
taste. It melts at 121°, and boils at 250°. 

It dissolves in 607 parts of water at 0°, and in about 12 
parts of boiling water. When boiled with a quantity of water 
insufficient to dissolve it, it melts. It volatilizes with the vapor 
of water. It dissolves readily in alcohol and in ether. When its 
vapor is passed over red-hot pumice-stone, contained in a porce- 
lain tube, it is decomposed into carbonic anhydride and benzene, 
CWO' = CO^ + C'W 

When heated with phosphorus pentachloride, it yields ben- 
zoyl chloride. 

C^H^O.OH -f PCP = POCP + HCl + C^H^O.Cl 



HIPPURIC ACID. 707 

The metallic and ethereal salts of benzoic acid are analo- 
gous to those of acetic acid. 

Benzamide, C*^H^-CO.NHl— This body is formed by the 
action of ammonia gas on benzoyl chloride. 

C^H^CO.Cl + 2Nff = NH^Cl + C^H^-CO.NH^ 

It is also formed by the action of ammonia on ethyl benzoate. 

Ethyl benzoate. Alcohol. Benzamide. 

It occurs in brilliant, colorless, oblique rhombic crystals, 
fiisible at 128°, and can be sublimed without decomposition. 
It is soluble in hot water and in alcohol. 

Benzophenone, or Diphenyl-ketone, C^^H^^O = C^H^- 
CO-C'H^. — This body is formed, together with benzene, in 
the destructive distillation of calcium benzoate (Chancel). 

Ca(C«H5-C0^)^ = CaCO^ + (C'WyCO 

Calcium benzoate. Diphenyl-ketone. 

It is also obtained by the action of carbonyl chloride upon 
benzene in the presence of aluminium chloride (Friedel and 

Crafts). 

2C«H« -f COCP = 2HC1 + (C^m)^CO 

It forms large, colorless, or slightly yellow, right rhombic 
prisms, fusible at 48-49°, and boils at 295°. It is insoluble 
in water, but very soluble in alcohol. 

Acetophenone, or Methylphenyl-ketone, CH^-CO-C^H^, 
melts at 20°, and boils at 202°. It is used in medicine as a 
soporific under the name hypnone. 



HIPPURIC ACID. 

CH^.NHrC^H^O) 
C.H«NO' = io.OH 

Hippuric acid is an important benzoic derivative. Hydro- 
chloric acid decomposes it into benzoic acid and glycocoll. 

C^H^NO^ + H^O = C^H^NO^ + C^H«0'^ 

Hippuric acid. Glycocoll. Benzoic acid. 

Rouelle, Fourcroy, and Yauquelin discovered this acid in 
the urine of the horse, but confounded it with benzoic acid. 
Its true nature was recognized by Liebig in 1830. Dessaignes 



708 



ELEMENTS OF MODERN CHEMISTRY. 



has made its synthesis by the reaction of benzoyl chloride on 
the zinc compound of glycocoll. 



Glycocoll. 



+ C^ffO.Cl = 

Benzoyl chloride. 



C^HXC'H50)N0' + HCl 

Hippuric acid. 



Hippuric acid is obtained from the urine of horses and cows 
by mixing the urine with 2 or 3 times its volume of concen- 
trated hydrochloric acid. The hippuric acid separates in col- 
ored crystals. 

When properly purified, it crystallizes in long, colorless 
prisms, but slightly soluble in cold water, very soluble in boil- 
ing water and in alcohol. When heated in a retort, it decom- 
poses and yields a sublimate of benzoic acid. At the same 
time a certain quantity of an oily body having a disagreeable 
odor distils: it is phenyl cyanide, or benzonitrile, CN.C^H^ 

SALICYLALDEHYDE (OUTHOXYBENZALDE- 
HYDE. 

C7H602 = C6H4(OH).CHO 

This compound, which is isomeric with benzoic acid, exists 
naturally in the essential oil of the meadow-sweet {Spirsea ul- 
marid). Piria obtained it by oxidizing salicin by potassium 
dichromate and sulphuric acid (page 658). 

It is also formed by the action of chloroform on phenol in 
presence of caustic soda (page 679). 

It is a colorless, highly refracting liquid, and boils at 196.5°. 
Its density at 13.5° is 1.173. Its odor is pleasant and its 
taste burning. It is quite soluble in water, and dissolves in 
alcohol and ether in all proportions. It has an acid reaction. 
It produces a violet color with ferric chloride. Oxidizing 
agents convert it into salicylic acid. 

^ ^ ^-CHO + ^ — ^ ^ <CO.OH 

By the action of fused potassium hydroxide, it is likewise 
transformed into salicylic acid, with disengagement of hydrogen. 
(^70602 _^ KOH = KC^H^O^ + H^ 

Salicyl aldehyde. Potassium salicylate. 

Saligeninol. — In presence of sodium amalgam and water, 
salicyl aldehyde fixes H^ and is converted into saligeninol 
(Beincke and Beilstein). 

Q7H602 _|. U2 ^ Q-'WO^ 

Salicyl aldehyde. Saligeninol. 



SALICYLIC (ORTHOXTBENZOIC) ACID. 709 

The latter body is also formed, according to Piria, by tbe 
decomposition of salicin by ferments and acids (page 658). It 
crystallizes in tables having a pearly lustre, or in small, brilliant 
needles. It may be made synthetically by the action of methy- 
lene chloride on sodium phenate (Greene). 

C«H5.0H + CH2C12 + 2NaOH = C6H*<^^2 qjj + 2NaCl + H20 

Phenol. Methylene Saligeninol. 

chloride. 



SALICYLIC (ORTHOXYBENZOIC) ACID. 

C7H603 = C6H4(OH).C02H 

Formation and Preparation. — This body was discovered 
by Piria, who obtained it, in 1839, by fusing salicyl aldehyde 
with potassium hydrate. 

C^H^O' + KOH = KC^H^O^ + H^ 

Oil of meadow-sweet contains it naturally, together with 
salicyl aldehyde. The essential oil of Gaidtheria procumhens 
(winter-green) is methyl salicylate (Cahours), that is, sali- 
cylic acid, in which the atom of basic hydrogen is replaced by 
methyl. 

Salicylic acid was formerly prepared by boiling oil of 
winter-green with caustic potassa as long as methyl alcohol 
is disengaged. Potassium salicylate is formed, and is after- 
wards decomposed by an excess of hydrochloric acid. The 
salicylic acid separates, and is purified by recrystallization 
from boiling water. 

Kolbe and Lautemann formed salicylic acid by synthesis by 
passing carbon dioxide into phenol in which sodium was dis- 
solved. Sodium salicylate is thus formed. 

C«H^OH -f CO.O =. C'H*(OH) 

CO.OH 

Phenol. Salicylic acid. 

Kolbe and Schmitt have improved this process, and large 
quantities of salicylic acid are now manufactured by treating 
dry sodium phenate with carbon dioxide under pressure, and 
heating the product to 130°. According to Schmitt, sodium 
pTienylcarhonate^ C^H^O.COONa, is first formed, and upon 

60 



710 ELEMENTS OF MODERN CHEMISTRY. 

heating under pressure tbis is converted into sodium sali- 
cylate. 

Sodium phenato. Phenol. Sodium-salicylate of sodium. 

After removing the excess of phenol by distillation, the 
mass is exhausted with water, and the solution is treated 
with hydrochloric acid, which sets free the salicylic acid. 

Properties. — Salicylic acid crystallizes from its alcoholic 
solution in large, monoclinic prisms, and from its aqueous 
solution in long needles. It melts at 156°. When mixed with 
pumice-stone and rapidly distilled, it breaks up into carbon 
dioxide and phenol. 

It is very soluble in alcohol and ether, and in boiling water, 
but cold water scarcely dissolves it. Its aqueous solution pro- 
duces a deep violet color with the ferric salts. 

When salicylic acid is treated with nitric acid, it is converted 
into two isomeric nitrogenized acids ; both are nitrosalicylic 
acids, C^H5(NO'0Ol 

«-nitrosalicylic acid crystallizes in long, colorless needles, 
which are anhydrous and melt at 228° ; they are very slightly 
soluble in cold water. It produces a blood-red color with ferric 
chloride. 

/?-nitrosalicylic acid crystallizes in long, colorless needles, 
containing one molecule of water of crystallization. When 
heated, it loses this water and melts at 144-145°. It is slightly 
soluble in cold water. Its solution also produces a blood-red 
color with ferric chloride. This acid is also formed when 
indigo is long boiled with nitric acid. It was formerly called 
indigotic acid. 

Salicylic acid possesses antiseptic properties like phenol, 
without presenting the same inconveniences as the latter as 
regards odor and causticity. 

Methyl Salicylate, C'H^(CH0Ol— Cahours first recognized 
the oil of GauUherta, known as essence of winter-green, to be 
methyl salicylate. When purified, this body forms a colorless 
oil, having a pleasant odor. It boils at 223.7°. Its density at 
0° is 1.1969. Like the phenols, it has the characters of a 
weak acid. When a concentrated solution of potassium hy- 
drate is added to methyl salicylate, a precipitate of potassium 



ANISIC ALDEHYDE AND ACID. 711 

gaultherate is formed. Cahours discovered tlie existence of an 

isomeride of methyl salicylate. It is methylsalicylic acid. The 

following formulae indicate the constitutions of these bodies : 

C6H*.0H C6H4.0H C6H4.0K CeH^.OCHS ceH^.OCH^ 

CO.OH C0.0CH3 C0.0CH3 CO.OH C0.0CH3 

Salicylic acid. Methyl Potassium Methylsalicylic Methyl 

salicylate. gaultherate acid. methylsalicylate. 

METOXYBENZOIC AND PAROXYBENZOIC ACIDS. 

These two acids are isomeric with salicylic acid. 

Metoxybenzoic acid is formed under various circumstances ; 
especially when metachloro-benzoic acid, a chloro-derivative of 
benzoic acid, is heated with potassium hydrate. 

C^ffClO^ + 2K0H = Gm\OK)0' + KCl + H^O 

It is an anhydrous, crystalline powder, consisting of small, 
square tables. Sometimes it is in mammillated crystals. It melts 
at 200°, and can be distilled without alteration. It is only 
slightly soluble in cold water, but dissolves more readily in boil- 
ing water. 

Paroxybenzoic Acid is formed under rather remarkable cir- 
cumstances. We have already seen that in presence of sodium, 
phenol fixes carbon dioxide, forming sodium salicylate. If the so- 
dium be replaced by potassium, the same reaction produces potas- 
sium paroxybenzoate. The same salt is formed when potassium 
phenate is heated to 210 or 220° in a current of carbon dioxide ; 
below 150°, only potassium salicylate is formed. 

Paroxybenzoic acid crystallizes in transparent, oblique rhom- 
bic prisms, containing one molecule of water of crystallization. 
When anhydrous, it melts at 210°, and is partially decomposed 
into phenol and carbon dioxide. It is much more soluble in 
water and alcohol than salicylic acid. Its aqueous solution 
does not produce a violet color with ferric chloride. 

ANISIC ALDEHYDE AND ACID. 
Anisic Compounds. — When the oils of anise, of fennel, or 
of tarragon are heated with nitric acid, they are converted into 
a colorless oil, having a spicy odor, and boiHng at 248°. This 
is anisic aldehyde, C^H^O^. By a more complete oxidation, 
this aldehyde is converted into anisic acid, C^H^O^. The latter 
crystallizes from hot water in long needles, and from alcohol in 
rhomboidal prisms. It melts at 185°, and distils without de- 
composition at about 280°. When heated with barium oxide, 



712 



ELEMENTS OF MODERN CHEMISTRY. 



C'JI*<C?,OH 

Paroxybenzoic acid. 



^^<CHO 

Methylparoxybenzoic, 
or anisic aldehyde. 



C02H C02H 

Propionic acid. Amidopropionic acid. 



it is decomposed into carbon dioxide and anisol (page 680). 
Anisic aldehyde and acid present very simple relations of com- 
position with paroxybenzoic acid. 

Anisic aldehyde is methylparoxybenzoic aldehyde, and anisic 
acid is methylparoxyhenzoic acid. 

^^<CO.OH 

Methylparoxybenzoic, 
or anisic acid. 

TYROSINE. 

This body seems to be related to the preceding compounds. 

It may be regarded as amidopropionic acid in which one atom 

of hydrogen is replaced by the group CH^.OH (paroxyphenyl) 

as it exists in paroxybenzoic acid. 

C2H5 C2H*(NH2) C2H3(C6H4.0H)(NH2) 

C02H 

Oxyphenyl-amidopropionic 
acid (tyrosine). 

Tyrosine is the product of the decomposition of many nitro- 
genized matters in the animal economy. It may be prepared 
by boiling for sixteen hours 1 part of horn shavings with 2 
parts of sulphuric acid diluted with 4 times its volume of water. 
The liquid is then neutralized with milk of lime, filtered, the 
filtrate evaporated to half its volume, acidified with sulphuric 
acid, and treated with an excess of lead carbonate. 

The solution, which contains the tyrosine as lead salt, is de- 
composed by hydrogen sulphide, filtered, and evaporated. The 
tyrosine crystallizes out, and may be purified by several crystal- 
lizations. The mother-liquors contain leucine. 

Tyrosine crystallizes in long, colorless needles, often united 
in tufts. It is but slightly soluble in water and in cold alcohol, 
more soluble in hot alcohol, and insoluble in ether. It forms 
definite compounds with both acids and bases. When fused 
with potassium hydrate, it breaks up into paroxybenzoic and 
acetic acids, and ammonia. 

Tyrosine may be recognized by the following reaction. 
When its aqueous solution is boiled with a solution of mer- 
curic nitrate, as neutral as possible, a voluminous yellow precip- 
itate is formed, which assumes a deep copper-red color by 
boiling with nitriv acid containing a small quantity of nitrous 
acid. 



GALLIC ACID. 713 

GALLIC ACID. 

C7H605 = C6H2(OH)3 - CO.OH 

This acid is closely related to salicylic acid. It is dioxysali- 
cylic acid, and Lautemann obtained it by treating di-iodosali- 
cylic acid with alkalies. 

QTjjipQs _p 2K0H = 2KI + C^H*(0H)20' 

Di-iodosalicylic acid. Gallic acid. 

We have already seen that gallic acid is a product of the 
decomposition of tannic acid. It is prepared by exposing 
coarsely-powdered and moistened nut-galls to the air, renewing 
the water as it evaporates. At the end of two or three months 
a black liquid is separated from the mass by strong pressure, 
and the solid residue is exhausted with boiling water, Gallic 
acid crystallizes out on the cooling of the filtered liquid. It is 
purified by several crystallizations in boiling water. 

Gallic acid forms long, silky needles, which contain one 
molecule of water of crystallization. It has no odor ; its taste 
is astringent and slightly acid. When heated to 220° it melts, 
and losing carbon dioxide is converted into pyrogallol^ or pyro- 
gallic acid. 

C'H^O^ = CO'^ + C^H^OHy 

Gallic acid. Pyrogallol. 

Gallic acid dissolves in 100 parts of cold water, and in 3 
parts of boiling water. It is very soluble in alcohol, less soluble 
in ether. Its solution gradually absorbs oxygen when exposed 
to the air, and at the same time becomes colored and disengages 
carbon dioxide. 

If a recently boiled solution of gallic acid be passed up into 
a tube filled with mercury and containing no air, and some 
recently boiled baryta-water be then added, a white precipitate 
is formed which at once changes to blue, if a few bubbles of 
oxygen be introduced. The change of color is the indication 
of an oxidation of the gallic acid, favored in this case by the 
presence of the alkali. 

Pyrogallol, or Pyrogallic Acid, C^H^(OH)^, occurs in 
brilliant white laminae which melt at 115°. It is soluble in 
water, sparingly soluble in alcohol and ether. It is a power- 
ful reducing agent : gold, silver, and mercury are precipitated 
by it from their solutions. Dissolved in an excess of potash 
lye, pyrogallol energetically absorbs oxygen. This solution 

60* 



714 ELEMENTS OF MODERN CHEMISTRY. 

is employed for tlie rapid estimation of oxygen in air and 
other gaseous mixtures. 

The peculiar reducing properties of pyrogallic acid render 
it one of the best photographic developers. 



XYLENES AND DERIVATIVES. 

C8Hio=C6H4(CH3)2 
That portion of coal-tar which boils between 136 and 139° 
contains a mixture of isomeric hydrocarbons, which is desig- 

QJJ3 

nated as xylene. It is dimethylbenzene, C^H*<CnTT3,andcan 

exist in three different isomeric modifications, like all of the 
di-substituted derivatives of benzene. 

MetaxT/lene, which boils at 137°, predominates in the mixture 
of xylenes which is obtained from coal-tar. When oxidized by 
chomic acid, it is converted into isophthalic acid, C^H*(CO^H)l 

Orthoxylene is a colorless liquid, boiling at 140-141°. Ni- 
tric acid oxidizes it to orthotoluic acid and further to phthalic 
acid. 

Paraxylene is solid, and crystallizes in oblique rhombic 
prisms, fusible at 15°. It boils at 136-137°. Dilute nitric 
acid converts it into paratoluic acid. Chromic acid oxidizes it 
to terephthalic acid. 

There are very many derivatives allied to these isomeric 
xylenes. One or more atoms of hydrogen may be replaced, 
either in the benzene nucleus or in the methyl chains, by chlo- 
rine, bromine, or by groups such as OH, NO^, NH^, etc. The 
methyl chains may be oxidized by boiling the xylenes with nitric 
or chromic acid, as indicated above. In this case the group 
CH^ is replaced by the carboxyl group CO. OH, and the hy- 
drocarbons, C'^H*(CH^)^, are converted into either toluic acids 
or phthalic acids, of each of which there are three isomerides. 

c«H*<cg c^HK^^OT ^^'<'S;^ 

Xylenes. Toluic acids. Phthalic acids. 

We cannot describe all of these bodies here, but must limit 
ourselves to a brief description of phthalic acid and its isomer- 
ides. 



PHTHALIC ACIDS. 715 



PHTHALIC ACIDS. 

C8H604 = C6H4(CO.OH)2 
Ordinary, or Orthophthalic Acid. — Laurent obtained this 
acid by boiling naphthalene for a long time with nitric acid. It 
crystallizes in brilliant scales, or in short, thick prisms, which 
are but slightly soluble in cold water, very soluble in hot water, 
alcohol, and ether. It melts at 213°, and loses the elements 
of water, being converted into phthalic anhydride. 
C6H4<g^.OH ^ JJ20 + C6H*<^0>^0 
Phtbalic acid. Phthalic anhydride. 

Phthalic anhydride crystallizes in long, brilliant prisms, 
fusible at 127°-128°. It boils at 284°. It possesses a remarka- 
ble property, which was discovered by A. Baeyer, and which^is 
now applied practically in the arts. When heated with the 
phenols, it combines with them directly with elimination of the 
elements of water, and compounds are obtained which are 
designated as jjhthaleins. 

Thus, when phthalic anhydride is heated with ordinary 
phenol, two molecules of phenol combine with one molecule 
of phthalic anhydride, with elimination of one molecule of 
water, and the phthalein of phenol is obtained. 

CO C6H5 0H /C = C(C6H*.0H)s 

Phthalic anhydride. 2 mol. phenol. Phenolphthalein. 

Pheriolphthalein occurs as a yellowish crystalline powder. 
It melts at 250° and dissolves readily in alcohol. Its solu- 
tion turns pink with the slightest trace of free alkali ; hence 
it is used as an indicator in alkalimetry. 

When resorcinol is heated with phthalic anhydride, two 
molecules of water are eliminated, and a body is obtained to 
which Baeyer has given the nsnae fluorescein. 

Phthalic anhydride. 2 mol. respijcinol. Fluorescein. 

Fluorescein forms orange-red, crystalline grains, insoluble 
in cold water, and but slightly soluble in boiling water. It 
dissolves readily in solutions of the alkalies and alkaline 



716 ELEMENTS OF MODERN CHEMISTRY. 

carbonates. Its dilute solutions are yellow, and have a mag- 
nificent green fluorescence. Hence tlie name fluorescein. 

Tetrahromo-fluorescein, C^^H^Br^O^, is employed in dyeing 
under the name eosin. It communicates to silk a beautiful 
rose-red tint. 

Terephthalic Acid. — Cailliot obtained this body by sub- 
mitting oil of turpentine to a long ebullition with dilute 
nitric acid. The same acid is formed by the oxidation of 
paraxylene and its derivatives by potassium dichromate and 
sulphuric acid. It is a white powder, almost insoluble in 
water, alcohol, and ether. It sublimes without melting and 
without decomposition. 

Isophthalic Acid is formed by the oxidation of metaxy- 
lene or metatoluic acid. Long, thin, colorless crystals, slightly 
soluble in water, soluble in alcohol, and fusible above 300°. 
It may be sublimed without decomposition. 



TRIMETHYL-BENZENES AND ISOMERIDES. 

The hydrocarbons C^H^^ may be derived from benzene by the 
substitution : 1, of three methyl groups for three atoms of 
hydrogen ; 2, of a methyl and ethyl group for two atoms of 
hydrogen ; 3, of a propyl or isopropyl group for one atom of 
hydrogen. 

Their constitutions are then thus expressed : 

C^H^CCH^)^ C«H^<^2H5 C^H^-C^H^ 

TrimethylbenzeneSo Methyl-ethyl benzenes. Propyl and isopropyl benzenes. 

Trimethylbenzenes. — The methyl groups may be arranged 
in three difi"crent ways, and three isomers of position are 
actually known. 

Mesitylene^ C^H^^CH^(^), the symmetrical trimethylbenzene, 

is obtained by distilling acetone with an equal measure of sul- 
phuric acid diluted with half its volume of water : the reaction 
is moderated by adding sand to the mixture. 

Mesitylene is a liquid having a pleasant odor, and boiling at 
163°. When boiled with dilute nitric acid it is oxidized, and 
forms successively three acids, in which one, two, or all of the 
methyl groups are converted into carboxyl. 



CYMENE AND ITS DERIVATIVES. 717 

/CH^C) /CH^ /CW /CO.OH 

^GWC) ^CO.OH ^CO.OH ^CO.OH 

Mesitylene. Mesitylenic acid. Mesidic Trimesic acid. 

or uvitic acid. 

With concentrated nitric acid it yields nitro-derivatives. 
Pseudocumene, or asymmetrical trimethylbenzene, 

C^H^^CH^(^), exists, together with mesitylene, in coal-tar, 

\CHXO 
but cannot be separated by fractional distillation. It is ob- 
tained synthetically by treating a mixture of bromoparaxy- 
lene and methyl iodide with sodium. It boils at 169°. 

Hemimellithene, C^H^^CH^O, has the methyl groups in 

adjacent positions, and is produced when bromometaxylene, 

(1) (2) (3) 

C^H^CH^BrCff, is made to react with methyl iodide and 
sodium (Jacobsen). It boils at 175°. 

Cumene, or Isopropylbenzene, C^H^-C^H^', was obtained by 
Gerhardt and Cahours by distilling cuminic acid with lime. 

Cuminic acid. Cumene. 

Its synthesis has been made by the action of isopropyl iodide 
on benzene, in presence of aluminium chloride. 

C^H« H- CH^-CHI-CH^ = HI + C^H5-CH<^^3 

It is a colorless liquid, boiling at 151°. 

CYMENE AND ITS DERIVATIVES. 

Cymene, which is a product of the dehydration of camphor, 

is methylisopropylbenzene. Its synthesis is made by the ac- 
tion of sodium on a mixture of parabromisopropyl benzene 
and methyl iodide (Widman). 

It exists naturally in the essential oil of Cuminum Cyminum^ 

which contains also cuminol, or cuminic aldehyde, C^H*<pTT/^- 

Together with thymol, it exists in oil of thyme. It may be best 



718 



ELEMENTS OP MODERN CHEMISTRY. 



prepared by distilling laurel camphor with phosphorus penta- 
chloride. 

Cymene is a liquid of an agreeable odor ; density at 0°, 
0.872. It boils at 175-176°. 

Upon oxidation with nitric acid it yields paratoluic acid ; 
chromic acid converts it into terephthalic acid. 

THYMOL, OR THYME-CAMPHOR. 

This compound, which is a phenol, presents certain analo- 
gies to the camphors (page 727). Thymol and its isomeride, 
carvacrol, are related to cymene, being oxycymenes. 

CHY^^ /CH^C) yQWQ) 

C«H*<^3TrvA C«H^f-OH(0 C^H^^OHC) 

^ ^ U Xc^HXO \C^HXO 

Cymene. Thymol. Carvacrol. 

Thymol exists, with cymene and thymene (C^°H^^), in oil 
of thyme (^Thymus serpyllum)^ and in the essential oils of 
Ptychotis ajowan and Monarda punctata. It is prepared by 
treating these oils with potassium hydrate solution, separating 
the insoluble hydrocarbons, and precipitating the alkaline 
solution with hydrochloric acid. 

Thymol crystallizes in large colorless plates, fusible at 44°, 
and boiling at 230°. It possesses antiseptic properties. 



TERPENES AND CAMPHORS. 

Closely related to cymene are a number of hydrocarbons 
of the composition (C^H^)°, known as the ferpenes, and their 
oxygenized derivatives, the camphors. Both groups of com- 
pounds are widely distributed in nature. 

The terpenes proper are represented by the formula C^°H^^. 
They form the basis of many essential oils, such as the oils 
of turpentine, lemon, orange-peel, bergamot, juniper, savin, 
elemi, eucalyptus, etc. 

At low temperatures some of these deposit oxygenized 
solid bodies that were formerly designated as stearopteiies, 
but are now classed with the camphors. 

Essential Oils. — These volatile liquids are generally ob- 
tained by distilling the vegetable products which contain 
them with water, for, although their boiling-points are be- 



TERPENES AND CAMPHORS. 



719 



tween 150 and 200°, they distil readily with aqueous vapor, 
and collect in the jPorm of a layer on the surface of the 
condensed water. 

The more ordinary process consist-s in passing a current of 
steam through the plants or aromatic vegetables. For this 
purpose they are placed on a diaphragm, M (Fig. 134), which 




(0) 



^ 




Fig. 134. 



is fixed above the bottom of an ordinary still. The head of 
the still is then adjusted, connection is made with a condenser, 
and a current of steam is passed in by the tube TT'T", which 
penetrates into the still. The steam carries with it the essen- 
tial oil, which diffuses in it by virtue of 
the high tension of the vapor of these oils at 
100°. The mixed vapors rise into the head 
of the still and condense in the condensing 
worm. The condensed water, generally 
clouded by little drops of the essential oil, 
is received in a vessel of peculiar form, 
which is called a Florentine receiver. It is 
shaped like an ordinary flask (Fig. 135), 
having at its bottom a tube which curves 
upwards, in the form of a swan's neck, and 
the upper part of which is but little below 
the mouth of the flask. As the condensed water and oil collect 
in this ingenious apparatus, the oil separates and floats on the 
water ; as the distillation continues, the liquid rises not only in 
the flask, but in the lateral tube, until the water, which is 
always in large excess, reaches the level of the curved neck 
and flows off alone, the lighter oil accumulating in the flask. 




Fig. 135.4 



720 ELEMENTS OP MODERN CHEMISTRY. 

OIL OF TURPENTINE. 

The most important of the essential oils is oil of turpen- 
tine, which is obtained by distilling the turpentine of com- 
merce with water. Turpentine is a mixture of resin and 
essential oil, and flows from incisions cut in the trunks of 
trees of the genera Pinus, Abies, Ficea, Larix. 

When this resinous substance is distilled with water, the 
oil passes over and the resin remains ; the latter is called 
colophony, or rosin. 

Oil of turpentine is a colorless, mobile liquid, having a 
peculiar odor, and boiling at 158°. Its density at 16° is 
0.870. It is insoluble in water, but miscible in all propor- 
tions with alcohol and ether. According to their origin, the 
turpentines exhibit certain peculiarities, especially in their 
action upon polarized light. The following are the most 
important varieties : 

1. American oil of turpentine is obtained from the turpen- 
tine of Pinus palustris. It rotates the plane of polarization 
to the right. 

2. English oil of turpentine (australene) is derived from 
Pinus australis, and is likewise dextro-rotatory. 

3. French turpentine comes from the Pinus maritima ; it 
yields an oil which turns the plane of polarization to the left. 

4. German oil of turpentine is distilled from the turpentine 
of Pinus syhestris. It is levo-rotatory. 

5. Venetian oil of turpentine comes from the exudation of 
Larix europsea, and is levo-rotatory. 

Metamorphoses of Oil of Turpentine. — 1 . When exposed to 
the air, oil of turpentine gradually absorbs oxygen, becomes 
yellow and partly resinified. This slow oxidation is due to 
the production of ozone, with which the oil becomes charged ; 
it then possesses oxidizing properties (page 71). 

2. If vapor of oil of turpentine be passed through a red- 
he^ porcelain tube, it is decomposed, yielding isoprene, C^W, 
cymene, benzene, toluene, xylene, and higher hydrocarbons. 

3. Concentrated nitric acid oxidizes oil of turpentine with 
such energy that the mixture sometimes takes fire. When 
boiled with dilute nitric acid, it forms paratoluic, terephthalic, 
and oxalic acids. 

4. When a mixture of alcohol, nitric acid, and oil of tur- 
pentine is left to itself for some time, the latter substance 



TERPENES. 721 

fixes the elements of three molecules of water and is con- 
verted into a crystallized solid body, Cm^'O' + H^O, called 
terpin hydrate. If this hydrate be heated to 100°, it loses 
water and is converted into a crystalline mass, fusible at 
117° : this is terpin. 

5. When oil of turpentine is mixed with -^ its weight of 
concentrated sulphuric acid, and the mixture is agitated, it is 
converted into terehene, an optically inactive mixture of ter- 
penes, which boils at 156°, and a polymeric hydrocarbon, 
Q2ojj32^ which boils between 310 and 313° (H. Deville). By 
reason of the reducing action which the oil of turpentine 
exerts on the sulphuric acid, and which produces sulphurous 
oxide and water, two atoms of hydrogen are removed from 
the molecule C^*'!!^®, and, independently of terebene, a certain 
quantity of cymene^ C^°H^*, is formed (Riban). 

C^ojjie _^ go^H^ z= C^^H^^ + SO^ + 2H20 

6. The halogens act energetically upon oil of turpentine. 
At low temperatures it combines with chlorine and bromine, 
forming di-halogen addition products, and these upon warm- 
ing give oif two molecules of hydrochloric or hydrobromic 
acid, and are converted into cymene. 

Q^'W^ + CP = C^^'Hi^CP 
(.10H16QP ^ Q10H1* _l_ 2HC1 

This conversion of turpentine into cymene is most readily 
effected by heating it with iodine. 

7. Oil of turpentine combines with the halogen acids. 
Some of the terpenes occurring in turpentine combine with 
only one molecule of hydrochloric acid, whilst others form 
addition products with two molecules (see below). 

TERPENES. 

Of the hydrocarbons having the composition C^'^H^^, the 
following have been isolated : 

Pinene. — This is the chief constituent of the common 
varieties of oil of turpentine ; it is also met with in a large 
number of other essential oils. It exists in two optically 
active modifications : American oil of turpentine contains 
dextro-pinene, while the pinene of French turpentine is levo- 
rotatory. 

2f vv 61 



722 



ELEMENTS OF MODERN CHEMISTRY. 



Pinene combines with only one molecule of hydrochloric 
acid, forming the hydrochloride C^^H^^.HCl. This is a solid 
melting at 125° and boiling at 208°. It smells like camphor' 
and was formerly called artificial camphor. 

Addition products of pinene with two atoms of chlorine 
and bromine are also known. 

Camphene. — Camphene is an artificial product, and is the 
only terpene which is solid at ordinary temperatures. It 
results from the elimination of hydrochloric acid from pinene 
hydrochloride, and is readily prepared by heating hornyl 
chloride, C^'H^^Cl, with aniline. The melting-point of cam- 
phene is 50°. Two optically active modifications of opposite 
rotatory power and an inactive camphene are known. 

Camphene forms a monohydrochloride, but does not appear 
to be capable of combining with the free halogens. 

Fenchene resembles camphene in many respects. It was 
obtained by Wallach by heating fenchyl chloride, an isome- 
ride of bornyl chloride, with aniline. Its odor recalls that 
of camphene. Unlike the latter it does not solidify at low 
temperatures. It combines readily with one molecule of 
hydrochloric acid and with two atoms of bromine. 

Limonene is present in many essential oils, especially in 
the oils of orange-peel, lemon, and bergamot. Two active 
varieties — dextro- and levo-limonene — have been obtained. 
This terpene boils at 175°. Its density at 20° is 0.846. It 
combines with only one molecule of dry hydrochloric acid, but 
the resulting compound, C^^H^^HCl, forms addition products 
when treated with moist hydrochloric acid or with bromine. 
Limonene tetrabromide melts at 105°. 

Bipentene is an optically inactive limonene, resulting from 
the combination of the dextro- and levo-varieties. It is formed 
when either of these varieties, or when pinene or camphene 
is heated to 250°-300°. It is also produced in the distillation 
of caoutchouc, and occurs naturally in oil of elemi. Its 
chemical properties are identical with those of the active 
limonenes. 

Dipentene, as well as the limonenes, form characteristic 
combinations, C^^H^^ NOCl, with nitrosyl chloride: these 
nitrosochlorides upon boiling with alcohol are converted into 
the corresponding carvoximes, C^"H^^NOH. 
^ Sylvestrene occurs in Swedish and Kussian oils of turpen- 
tine. Its characters are very like those of the limonenes. 



TERPENES. 723 

It is dextro-rotatory, as is also its dihydrochloride, which 
melts at 72°. 

Phellandrene. — This terpene is found in oil of fennel and 
in certain eucalyptus oils. It boils at 170° and rotates the 
plane of polarization to the right. 

When a solution of phellandrene in petroleum ether is 
agitated with a solution of sodium nitrite, and acetic acid 
is gradually added, a voluminous crystalline mass of phel- 
landrene nitrosite^ C^^H^^.N^O^ separates. This rather un- 
stable body is highly characteristic ; its melting-point is 102° 
(Cahours, Wallach). 

Terpinene is formed by an intramolecular rearrangement 
of other terpenes, and occurs in oil of cardamom : it boils about 
180°, and forms a characteristic nitrosite fusible at 155°. 

Terpinolene is obtained by heating pinene with sulphuric 
acid. It boils about 185°. The tetrabromide melts at 116°. 

Dihydrocymene, which has been made synthetically by 
Baeyer, boils at 174°, and closely resembles some of the 
natural terpenes. 

Of the other hydrocarbons which are included in the ter- 
pene group, only a few can be mentioned here. 

Isoprene, C^H^, belongs to the hemiterpenes. It is pro- 
duced in the destructive distillation of caoutchouc, and 
readily polymerizes to dipentene. Isoprene boils at 37°. 

Cedrene and Cubebene, C^^H^*, represent the sesquiter- 
pe7ies. They boil between 250 and 260°, 

Caoutchouc (C^H'*)''. — This polyterpene is contained in the 
sap of many plants. It is obtained in an impure condition 
by allowing the " milk" of certain tropical trees {Syphonia^ 
Ficus elastica) to become solid. When fresh it is colorless 
and extremely elastic, but upon exposure to air and light it 
becomes dark and brittle. 

Pure caoutchouc cannot be melted without decomposition. 
It is insoluble in water and in alcohol, but soluble in ether, 
carbon disulphide, chloroform, and benzene. Its exact con- 
stitution is not known ; it is free from oxygen, and on dry 
distillation yields hydrocarbons (isoprene, dipentene, etc.). 

Caoutchouc acquires valuable properties when treated with 
sulphur. It is then said to be vulcanized. 

Grutta-Percha is obtained from the Isonandra-tree, and 
resembles caoutchouc in many respects, but is hard at ordi- 
nary temperatures, and contains oxygen. 



724 



ELEMENTS OF MODERN CHEMISTRY. 



ORDINARY CAMPHOR, OR LAUREL CAMPHOR. 

C10H16O 

Camphor exists in all the parts of Laurus camphora^ a 
tree occurring in Japan and China, and especially abundant 
in the Island of Formosa. When the wood is chipped and 
distilled with water, the camphor volatilizes and condenses in 
rice-straw, with which the heads of the stills in which the 
operation is conducted are filled. The product thus obtained 
in the form of small crystals, is refined by sublimation in 
glass vessels heated on a sand-bath. 

Artificially, camphor has been obtained by the oxidation 
of camphene and borneol. 

Camphor forms a semi-transparent, crystalline mass. Its 
odor is strong and aromatic ; its taste, bitter and burning. It 
melts at 175°, and boils and distils without alteration at 204°. 
Its density at 0° is 1.0. At ordinary temperatures, the ten- 
sion of its vapor is so great that it sublimes spontaneously in 
the vessels in which it is kept. 

Camphor is almost insoluble in water; when thrown in 
small fragments on the surface of that liquid, it executes gyra- 
tory movements. It dissolves in alcohol and ether, and the al- 
coholic solution rotates the plane of polarization to the right. 

A levo-rotatory modification of camphor results from the 
oxidation of levo-camphene, and occurs naturally in the oil 
of Matricaria parthenimn. 

Camphor is inflammable, and burns with a smoky flame. 
The following are its principal reactions : 

1. When heated with phosphoric anhydride, or with chlo- 
ride of zinc, it loses the elements of water and is converted 
into cymene. 



Qiojjieo 
Camphor. 



= H^O 



Cymene. 



2. The chemical behavior of camphor is that of a ketone. 
Although it does not fix hydrogen directly, it can neverthe- 
less be converted into a compound, C^°H^^O, which is borneol, 
or Borneo camphor. This is accomplished by the action of 
sodium, which replaces the hydrogen of a portion of the cam- 
phor, forming a sodium-camphor, while the displaced hydro- 
gen is fixed upon another portion of camphor (Baubigny). 



CAMPHOR. 725 

According to this reaction, corroborated by the inverse re- 
action, which will be indicated farther on, the same relations 
exist between borneol and camphor as between isopropyl 
alcohol and acetone. 

(.lojjieo C^°Hi«0 

Camphor, Borneol. 

3. Like other ketones, camphor reacts with phenylhy- 
drazine and with hydroxylamine, forming the hydrazone 
(.iojji6(]sr2HC«H^) and the oxime C^^H^'^CN.OH), respectively. 
Camphor oxime is readily prepared by heating camphor with 
hydroxylamine hydrochloride and sodium hydroxide in alco- 
holic solution (Auwers). It forms needle- like crystals which 
melt at 118°. 

4. When camphor is heated for a long time with a alco- 
holic solution of potassium hydroxide, it is decomposed into 
an acid and an alcohol, which is borneol (Berthelot). 

2C10JJ16Q _|_ KOH = C^'^H^^KO^ + C^^H^^O 

Camphor. Potassium camphinate. Borneol. 

5. When vapor of camphor is passed over soda-lime, heated 
to about 300°, the sodium salt of campliolic acid is obtained 
(Delalande). 

Q10H16O _^ NaOH = C^°H^WaO^ 

Camphor. Sodium campholate. 

6. When camphor is subjected to the action of aqueous 
hypochlorous acid, it is converted into monochloro-camphor, 
QiojjisQjQ^ which constitutes a colorless, crystalline mass, 
slightly soluble in water, freely soluble in alcohol and ether, 
and fusible at 95°. 

7. By the action of bromine on camphor at 100 or 120°, 
monohromo - camphor^ C^°H^°BrO, and clihromo - campho?-, 
Qiojju;gj.2Q^ are formed. These bodies crystallize in colorless 
prisms. The first fuses at 76°, the second, at 57°. 

A bromide of camphor, C^°H^*^OBr^, is also known; it is 
formed by the action of bromine on a solution of camphor in 
chloroform. It is a crystalline body which decomposes spon- 
taneously, especially by the action of light, losing hydrobromic 
acid and being converted into monobromo-camphor. 

8. Heating with iodine converts camphor into carvacrol 
or oxycymene (page 718). 

Qiojjieo -f P = C'WO + 2HI 

6l« 



726 



ELEMENTS OF MODERN CHEMISTRY. 



9. When camphor is boiled with nitric acid, it is oxidized 
and converted into camphoric acid. 

Q^^W^O + 30 = C^°H^W 

Camphor. Camphoric acid. 

By further oxidation this acid, which contains two carboxyl 
groups, is converted into the tribasic camplioronic acid. 
(.10JJ16Q4 _|_ 50 = C^^H^^O^ + CO' + H'O 

Camphoric acid. Camphoronic acid. 

Fenchone is the name given by Wallach to an isomeride 
of camphor which occurs in oil of fennel. It melts at 5° 
and boils at 192°. At 19° its specific gravity is 0.946. It 
is dextro-rotatory. 

Although soluble in concentrated nitric acid, it is but 
slowly oxidized even when boiled with a large excess of this 
acid. 

Fenchoneoxime forms beautiful crystals, melting at 161°. 

BORNEOL, OR BORNEO CAMPHOR. 

CioHisQ 

This camphor is extracted from the Dryohalanops aromatica^ 
a tree which grows in the Sunda Islands. Berthelot has ob- 
tained it by the action of an alcoholic solution of potash on 
ordinary camphor. It occurs in small, colorless, transparent, 
and friable crystals. Its odor recalls at the same time that of 
camphor and that of pepper. Its taste is burning. It melts 
at 206°, and boils at 212°. It turns the plane of polarization 
to the right. It is insoluble in water, but dissolves readily in 
alcohol and in ether. When treated with cold, fuming nitric acid, 
it loses H', and is converted into ordinary camphor, C^'^H^'^O. 

Gineol is isomeric with borneol. It is the chief constituent 
of the oils of cajeput and wormseed. It is a colorless liquid 
which boils at 176°. Its character is that of an oxide. 



MENTHOL, OR MINT CAMPHOR. 

Menthol is the solid part of the essential oil of mint 
(^Mentha piperita), in which it exists mixed with liquid ter- 
penes. It is deposited in crystals when oil of mint is cooled. 



CONSTITUTION OF THE TERPENES AND CAMPHORS. 727 

It forms colorless crystals, fusible at 42°; it boils at 213°. 
It rotates the plane of polarized light to the left. Dehydrat- 
ing agents, such as phosphoric anhydride and zinc chloride, 
convert it into menthene, C^^W^, boiling at 165°. 

Constitution of the Terpenes and Camphors. — We have 
seen that, under certain conditions, the benzene nucleus is 
capable of forming addition compounds (page 672). Thus, 
by the action of chlorine or bromine upon benzene in sun- 
light, di-, tetra-, and hexa-halogen addition products are 
obtained, and by heating benzene with a large excess of 
strong hydriodic acid, it is converted into hexahydrobenzene, 
C*^H^^ In the latter case the benzene nucleus is said to be 
reduced, the six latent atomicities being satisfied with hydro- 
gen. When the nucleus is on\j partially reduced, that is to 
say when only two or four atoms of hydrogen are added, the 
"aromatic" character of the original substance is destroyed, 
and the derivatives deport themselves like unsaturated com- 
pounds of the fatty series. 

Now the terpenes of the formula C^°H^^ contain two atoms 
more of hydrogen than cymene, and they are readily con- 
verted into this hydrocarbon, or derivatives of it, by various 
reactions. Moreover, their behavior towards the halogens 
and halogen acids is that of unsaturated compounds. They 
must be considered as dihydrocymenes, and the existence 
of numerous isomerides is explained by assuming that the 
added hydrogens occupy different positions. According to 
Wallach, who has made a most careful study of this group, 
the structure of pinene and limonene, for example, may be 
thus represented : 

CH3 CH3 

I I 

c c 

/\ ^ /^^ 

HC CH S2C CH 

l\l I I 

H2C ^CH HC CH2 

\/ %/ 

CH C 

C3H7 C3H7 

Pinene. Limonene. 

The camphors are oxygenized derivatives of partially re- 
duced cymenes. Borneol contains the group CH.OH, and is 
derived from a tetrahydrocymene (dihydrocamphene). Ordi- 
nary camphor is the corresponding ketone. 



728 



ELEMENTS OF MODERN CHEMISTRY. 



Their constitutions are probably expressed by the formulae 
CH3 CH3 

d 6 



CH3 

I 
C 



HC CH.OH 

I I 
H2C CH2 



HC 
H2C 



CO 



CH2 



HC 

C3H' 
Borueol. 



HC 




H2C 

I CH3-C 
H2C 



CH2 



C3H7 



Camphor. 

Menthol appears to be an oxyhexahydrocymene. 
CAMPHOKIC ACID. 

This acid, which has long been known, is obtained by boil- 
ing camphor with dilute nitric acid. The camphor, which at 
first floats as an oily liquid, finally disappears, and camphoric 
acid deposits as the solution cools. It is purified by dissolving it 
in caustic soda solution and precipitating with hydrochloric acid. 

Camphoric acid crystallizes in colorless plates. It is only 
slightly soluble in cold water, but quite soluble in alcohol. It 
melts at 187°, and if heated above its fusing-point becomes 

CO 

converted into camphoric anhydride^ C^H^*<;pQ>>0, which 

sublimes in brilliant needles, fusible at 221°. 

CaC^^H^^O^ = CaCO^ + C^ff^O 

Calcium camphorate. Camphorone. 

Besides ordinary camphoric acid, which is dextro-rotatory, 
there are two other modifications, — levo-camphoric acid, ob- 
tained from matricaria camphor, and meso-campJioric acid, 
formed by the union of equimolecular quantities of the two 
active varieties. 

Camphoric acid is dibasic ; its calcium salt yields by dry distilla- 
tion the compound camphorone, C^H^^O, a liquid boiling at 208°. 

Camphoronic acid, CT^'^(COOH)^ is produced by the 
further oxidation of camphoric acid. It is a crystalline com- 
pound fusible at 135°. By its synthesis it was recognized as 

CH-^ C(CH^) C(CH-7 

trim^thyl-tricarballylic acid, 



C00^ COOH COOH 



UNSATURATED AROMATIC COMPOUNDS. 729 

Among the other benzene addition compounds we can 
mention only the following : 

Quercite, C^HXOH)^ — This compound is pentahydroxy- 
hexahydrobenzene, but was formerly considered to be related 
to the sugars, and was called acorn-sugar^ having been first 
obtained from acorns. It forms monoclinic crystals, fusible 
at 222°, and subliming at 235°. It is soluble in water and 
in dilute alcohol, and its solutions are dextro-rotatory, a fact 
which is easily explained, as it contains two similar asym- 
metric carbon atoms. Hydriodic acid converts it into ben- 
zene, and finally into hexyl iodide. 

Inosite, C^H^(OH)^ — In 1850, Scherer extracted a sweet 
substance from the muscles, and the same compound has 
since been found in the lungs, kidney, spleen, and liver. 
Under the name inosite it was long classified with the sugars, 
but Maquenne has shown that it is no other than hexahy- 
droxyhexahydrobenzene. 

Inosite forms large rhombic tables or transparent, color- 
less prisms having a sweet taste. The crystals contain one 
molecule of water of crystallization, and effloresce in the air. 
Inosite is soluble in water, but insoluble in absolute alcohol 
and in ether. It is optically inactive, is not fermentable, 
and will not reduce alkaline cupric solutions. 

Dambonite, C^H«(0H)XCH^)2.— This substance is the 
dimethyl ether of inosite, and was first obtained by A. 
Girard from Gaboon caoutchouc. It forms colorless needles, 
fusible at 190° and subliming at 210°. It is soluble in water, 
only slightly soluble in alcohol. Hydriodic acid reduces it 
to methyl iodide and inosite. 



UNSATURATED AROMATIC COM- 
POUNDS. 

The benzene derivatives so far considered are formed by 
the replacement of the hydrogen of benzene by saturated 
groups. There are, however, compounds which contain un- 
saturated groups, and which can so combine directly with 
chlorine, bromine, or hydrogen. Among these we will describe 
only styrolene and some of its derivatives, 



730 



ELEMENTS OP MODERN CHEMISTRY. 



STYEOLENE, OR PHENYLETHYLENE. 

C8H8 = C6H5-CH=CH2 

This compound, which may be considered as ethylene in 
which one atom of hydrogen is replaced by phenyl (C^H^), 
exists in storax, the thickened juice of the bark of Liquid- 
ambar orientate. It is extracted by passing steam through this 
balsam, fused under boiling water ; the styrolene is carried over 
with the steam. It is also formed when cinnamic acid is heated 
with lime ; for this reason it has been sometimes called cinna- 
mene. 

It is a colorless, mobile, strongly-refracting liquid, having an 
agreeable odor. The styrolene obtained from storax is optically 
active, a property which appears due to some impurity, for the 
hydrocarbon obtained artificially is inactive. Its density at 0° 
is 0.925, and it boils at 145°. When long kept, it becomes 
polymerized, and more rapidly if heated, into metastyrolene^ a 
transparent, amorphous mass, which is reconverted into styro- 
lene when distilled. 

Styrolene, being unsaturated, can combine directly with chlo° 
rine and bromine. The bromide, C^H^Br^, crystallizes in needles 
or plates, fusible at 74°. When heated with hydriodic acid, 
styrolene is converted into ethylbenzene. 

C^H5-CH=CH2 + 2HI ^ C^H^-CH^-CH^ + P 



CINNAMIC ALDEHYDE. 

C9H80 = C6H5-CH=CH-CHO 

Cinnamic aldehyde exists in the essential oils of cinnamon 
and cassia. It is formed during the distillation of a mixture 
of cinnamate and formate of barium, by a reaction similar to 
that which yields the fatty aldehydes under the same conditions. 
It is made synthetically by passing hydrochloric acid gas into a 
mixture of ordinary aldehyde and benzaldehyde. 

C6H5-CHO + CH3-CH0 = C6H5-CH=CH-CHO + H20 

Benzaldehyde. Aldehyde. Cinnamic aldehyde. 

Cinnamic aldehyde is a colorless oil, heavier than water. It 
has an aromatic odor. When exposed to the air it becomes 
oxidized into cinnamic acid. It reacts with hydroxylamine 
and phenylhydrazine, and forms a crystallizable compound 
with sodium acid sulphite, a property which permits of its 
ready separation from oil of cinnamon. 



CINNAMIC ACID. 731 

CINNAMYL ALCOHOL, OR STYEONE. 

O9H10O = C6H5-CH=CH-CH2.0H 

Styracin^ which may be extracted from storax, is a cinnamyl 
cinnamate, a compound of cinnamic acid and cinnamic alcohol, 
and may be readily saponified by potassium hydroxide. 
C^H^OIC^H^ + KOH = C^H^O^K + C^mOH 

Cinnamic alcohol crystallizes in brilliant needles, soluble in 
alcohol, and slightly soluble in water. It melts at 33°, and 
distils without change at 250°. 

CINNAMIC OR PHENYLACRYLIC ACID. 

C9H802 ^ C6H5-CH=CH-CO.OH 

This acid exists in Tolu and Peruvian balsams, in storax, 
and in certain gum benzoins. It is formed by the careful 
oxidation of cinnamic alcohol or aldehyde, and has also been 
obtained synthetically by heating benzaldehyde with acetic 
anhydride and dry sodium acetate. 

C'H^-CHO + CH^-COOH = H^O + C«H^-CH=CH-CO.OH 

According to Perkin, who discovered this important re- 
action, the condensation is caused by the dehydrating action 
of the sodium salt, but Fittig's researches render it probable 
that the latter enters into the reaction and the anhydride is 
the dehydrating agent. 

" Perkin's reaction" has been extensively applied in the 
preparation of unsaturated acids, especially of the homo- 
logues of cinnamic acid. 

Cinnamic acid is colorless and odorless. It crystallizes from 
hot water in fine needles, and from alcohol in large prisms. It 
melts at 133°. When rapidly heated, it distils almost without 
alteration at 290°. When distilled with lime, or heated to 
200° with water, it is decomposed, yielding styrolene and carbon 
dioxide. 

C9H802 = C02 + C8H8 

By fusion with potassium hydrate it is converted into acetic 
and benzoic acids. 

C6H5-CH=CH-CO.OH + 2K0H = CefiS-CO.OK + CH^-CO.OK + H2 
Concentrated nitric acid converts it into two isomeric nitro- 
cinnamic acids^ C^H^(NO^)0^ ; orthonitrocinnamic acid, fusible 
at 240°, and paranitrocinnamic acid, fusible at 288°, 



732 ELEMENTS OF MODERN CHEMISTRY. 

Cinnamic acid can fix directly two atoms of chlorine, bromine, 
or hydrogen, so forming saturated compounds. Sodium amal- 
gam converts it into Tiydrocinnamic or phenylpropionic acid, 
C^H^-CH^-CH^-CO.OH, a compound crystallizing in fine, 
colorless needles, fusible at 47.5°, and boiling at 280°. The 
following formula will show the relations between acrylic and 
propionic acids, on one hand, and on the other those between 
cinnamic and hydrocinnamic acids. 

CH2r=CH-C0.0H CH^-CH^-CO.OH 

Acrylic acid. Propionic acid. 

CH(C«H^)=CH-CO.OH CH2(CH15)-CFP-CO.OH 

Cinnamic acid. Hydrocinnamic acid. 

(Phenylacrylic.) (Piienylpropionic.) 

The cinnamates resemble the benzoates. Ferric chloride 
produces a yellow precipitate in their solutions. 

Phenylpropiolic Acid, C«H^-CeC-CO.OH, is formed 
when the dibrom-addition product of cinnamic acid, p/ie^iy?- 
dibromopropionic acid^ is boiled with alcoholic potash. 

C^H^-CHBr-CHBr-CO.OH = C^H^-CeC-CO.OH -|- 2HBr 

It crystallizes in needles which melt at 137°. At higher 
temperatures the acid is resolved into phenylacetylene and 
carbon dioxide. 

C«H^-CEC-CO.OH = C^H^-CeCH + CO^ 

The ortho-nitro-derivative has been used in the artificial 
preparation of indigo blue. 

INDIGO. 

C16H10N2O2 

Indigo is obtained from difi"erent species of the genus Indi- 
gofera ; it is also found in woad (^Isatis tinctorid), but is no 
longer extracted from this plant. 

In India, indigo is prepared by macerating the stems and 
leaves of the indigofera, collected at the time of flowering, with 
water, in vats where they are allowed to ferment. In 12 or 
15 hours the liquid is drawn off into other vats, where it is 
agitated so as to bring it in contact with the air, an opera- 
tion which occasions the formation of a blue precipitate. The 
brown liquor is then drawn off, and the deposit is boiled in 
copper vessels ; it is then pressed between cloths and cut into 
cubical pieces and dried. In this form the indigo is delivered 
to commerce. 



INDIGO. 733 

Indigo is not contained ready formed in tlie plants wticli 
serve for its manufacture. Schunck considers that these 
plants contain a substance analogous to the glucosides, indi- 
can, which is decomposed by fermentation into indigo, and 
indogludn, C^H^^O^ 

The indigo of commerce contains from 50 to 90 per cent, of 
coloring matter. It generally occurs in irregular masses, of 
which the shade varies from violet-blue to blackish-blue. The 
most valued varieties present a brilliant coppery reflection. 

Pure indigo is called indigotin. It may be obtained by 
heating the indigo of commerce in a current of hydrogen, or 
by subliming it in small quantities between two watch-glasses 
(Chevreul). It then forms right rhombic prisms. Indigotin 
is insoluble in water, in cold alcohol, and in ether, but dis- 
solves in hot oil of turpentine and in aniline. When care- 
fully heated, and in small quantity, it volatilizes, and its 
vapor density corresponds to the formula C^^H^^N^O^ 

Concentrated, or, better, fuming sulphuric acid dissolves 
indigo at 50 or 60°, forming a beautiful blue solution, which 
contains two acids, indigomonosulphonic acid^ C^^H^N^O^. 
SO^H, and indigodisidphomc or sidpJimdigotic acid^ C^^H^N^O^ 
(SO^H)^. The solution of indigo in sulphuric acid is used 
in dyeing ; it is prepared by dissolving indigo in a hot mix- 
ture of fuming and ordinary sulphuric acids. The blue solu- 
tion thus obtained is known as sulphate of indigo, Saxon 
blue, or composition blue. 

Indigo carmine is the soluble sodium salt of the disulphonic 
acid. It is employed in dyeing animal fibres. 

Boiling dilute nitric acid converts indigo into isatin. The 
concentrated acid converts it first into nitrosalicylic acid, 
C^ff (NO')O^ and then into picric acid. 

When heated with potassium hydrate, indigo is converted 
into anthranilic (orthamidobenzoic) acid^ C^H^(Nff)0^, or 
into salicylic acid, which is formed at the expense of the 
anthranilic acid. 

C^H5(NH2)0^ -f KOH = KC^H^O^ + Nff 

Anthranilic acid. Potassium salicylate. 

When indigo is distilled with potassium hydrate, aniline 
passes over, being formed at the expense of the anthranilic acid 
first formed. 

Anthranilic acid. Aniline. 

62 



734 ELEMENTS OF MODERN CHEMISTRY. 

Synthesis of Indigo. — Various reactions liave been discov- 
ered whicli are applicable to the synthesis of indigo. The 
most important of these are due to von Baeyer, to whom also 
belongs the honor of having first (1878) prepared indigo 
artificially. Only a few syntheses of indigo blue can be 
considered here. 

1. Isatin chloride, which will be described farther on, when 
dissolved in acetic acid and treated with zinc dust yields a 
colorless liquid, which, when exposed to the air, assumes a 
blue color, and deposits crystals of indigotin. Ammonium 
sulphhydrate effects the reduction more rapidly than zinc 
and acetic acid (Baeyer and Emmerling). 

2. There exists normally in human urine a compound which 
may also be prepared artificially, indoxylsulpliate of potassium. 
When it is heated in the air, or treated with feeble oxidizing 
agents, it is converted into indigo (Baumann and Tiemann). 

Potassium indoxylsulphate, C^H'^NO.SO^K, is a derivative 
of indoxyl^ C®H®(OH)N, and the conversion of the latter into 
indigo is represented in the equation, 

2C'H'^(0H)N + 0' = C'^ff^N^O^ + 2>W0 

Indoxyl. Indigo. 

3. A much better yield of indigo blue is obtained by the 
action of reducing agents upon orthonitrophenylpropiolic 
acid (Baeyer, 1880). 

C«H*(N02)CEC-CO.OH-f2H2 = Ci«ffW0^+2C0'-f 2H20 

o-nitrophenylpropiolic acid. 

For this purpose orthonitrocinnamic acid is converted into 
its dibromide and the latter boiled with alcoholic potash. 
The resulting nitro-acid, by careful treatment with glucose 
and potash, is reduced to indigo. The high price of the re- 
quired materials has caused this process of manufacture to 
be abandoned. 

4. Baeyer has made an interesting synthesis of indigo 

from orthonitrobenzaldehyde, C^H*<j^^Q2/2y. This com- 
pound reacts with acetone, in presence of sodium hydrate, form- 
ing a compound, C^'^H^NO^ which contains the elements of 
acetone and orthobenzoic aldehyde, less one molecule of water. 
C^H5(N0^)0 + C^H^O = C^''H^(N,0^)0 + H^O 

Orthobenzoic aldehyde. Acetone. Acetonic derivative of ortho- 

benzoic aldehyde. 



INDIGO. 735 

An excess of caustic soda converts this last body into acetic 
acid and indigo. 

5. According to Heumann, indigo is produced when 
phenylglycocoll is fused with potash. 

C^H^NH.CHICOOH + 0' = C^^H^WO"' 

Baeyer's researches indicate that the molecular structure 
of indigo is expressed by the following formula : 
C«H*-CO CO-C«H* 
HN 6=6_NH 

Indigo White, C'^H^^^^O^— This body, which was discov- 
ered by Chevreul in 1812, results from the action of nascent 
hydrogen on indigo. It is produced when the latter substance 
is submitted to the action of alkaline solutions in presence 
of reducing matters, such as sulphurous or phosphorous acid, 
hydrogen sulphide, zinc, ferrous hydroxide, or grape-sugar. 
C^^H^WO^ + H^ = C^^H^^N^O^ 

Indigo white is ordinarily prepared by introducing a mix- 
ture of indigo, ferrous sulphate, slaked lime, and water into a 
vessel, which should be entirely filled with the mixture and 
then hermetically sealed and allowed to stand for two days. A 
clear, alkaline solution is thus obtained, which is decanted, and 
supersaturated with hydrochloric acid, out of contact with the 
air. A deposit of indigo white is formed, and must be collected 
on a filter, rapidly washed with boiled water, and dried in a 
vacuum. 

The body thus obtained has a dirty-white color, and is with- 
out either taste or smell. It is insoluble in water, but dissolves 
with a yellow color in alcohol, ether, and alkaline solutions. 
On contact with air it absorbs oxygen, and is converted into 
indigo blue. Nitric acid rapidly brings about this transformation. 

Uses. — Indigo is largely used in dyeing. The principle of 
its application depends on the conversion of the indigo blue 
into indigo white by reducing agents. The reduced indigo 
white is soluble in alkaline solutions, and in this form is fixed 
on the fabrics : it is reconverted into indigo blue by exposure 
to the air. The mixture just indicated for the preparation 
of indigo white (ferrous sulphate, indigo, lime, and water) is 
most frequently employed. It constitutes what is known as 
the vitriol vat. 



736 ELEMENTS OF MODERN CHEMISTRY. 

Schiitzenberger and de Lalande have described a process 
of dyeing witb indigo, based on the employment of sodium 
hydrosulpbite as the reducing agent. 

ISATIN. 

This body was discovered by Erdmann and Laurent in 1841. 
It is a product of the oxidation of indigo by dilute nitric acid. 

Pure isatin crystallizes sometimes in large, dark, gold- 
colored prisms, sometimes in small, reddish-yellow prisms 
having a brilliant lustre. It is only slightly soluble in cold 
water and in ether, but more soluble in boiling water, and very 
soluble in alcohol. Its solutions are brown-red. As it contains 
a carbonyl group, CO, isatin forms, like other ketones, crys- 
tallizable compounds with sodium acid sulphite, hydroxyla- 
mine, and phenylhydrazine, Isatin gives a characteristic 
reaction with thiophene. When a trace of the latter is added 
to a solution of isatin in sulphuric acid, a blue solution is ob- 
tained from which water precipitates mdojohemn, C^^ffNOS. 
When distilled with potash, isatin yields aniline. 

C^H^NO^ + 4K0H = 2K2CO^ + C^H^N + H^ 

Isatin. Aniline. 

It dissolves in solutions of the alkaline hydroxides, forming 
violet solutions, which become yellow when boiled, the isatin 
being converted into isatic acid. 

c«H^NO' + H^o = cmmo' 

Isatin. Isatic acid. 

Synthesis. — Among various methods by which isatin may be 
prepared synthetically, the following, discovered by Baeyer, is 
most interesting : 

Orthonitrobenzoyl chloride is converted into a cyanide, which, 
by hydrolysis, yields orthonitrobenzoyl-carbonic acid. By re- 
duction of the latter, the corresponding amide, isatic acid, is 
obtained, and this is converted into isatin by dehydration. 

^^ <N02(2) ^^ <N02 ^^^ <-N02 ^ ^ <-N02 

Orthonitrobenzoic Orthynitrobenzoyl Orthonitrobenzoyl Orthonitrobenzoyl 
acid. chloride. cyanide. carbonic acid. 

C'H^<Nh"2^^'^^ — H^O = C«H*<^^^COH 

Isatic acid. Isatin. 



INDOL. 737 

By the action of chlorine, isatin yields substitution products 
These latter break up, like isatin itself, by the action of potas 
slum hydrate, yielding cMoranilines (Hofmann). 

C^H^CINO^ -f 4K0H = 2K2CO^ + C^H^CIN + H^ 

Monochlorisatin. Monochloraniline. 

When isatin is heated with phosphorus pentachloride, in pres- 
ence of benzene, isatin chloride is obtained. This may serve, as 
has been seen, for the synthesis of indigo. 

C6H*<^^^C0H + PC15= C6H4<^^^CC1 + POCP + HCl 
Isatin. Isatin chloride. 

Products of the E-eduction of Isatin. — To isatin are re- 
lated certain products of its reduction, which are interesting 
and which have been studied by Knop and Baeyer. They are 

Dioxindol C8H7N02; 
Oxindol C8H7NO ; 
Indol CSH^N. 

Isatic acid, which has been mentioned, may be considered as 
trioxindol, C^H^NOl Dioxindol and oxindol are formed suc- 
cessively by the action of sodium amalgam on an aqueous solu- 
tion of isatin. 

C^H^NO' + H2 = C^H^NO^ 

Isatin. Dioxindol. 

C«H^NO^ + H^ = C«H^NO + H^O 

Dioxindol. Oxindol. 

INDOL. 

C837N = C6H^<^^>CH 

By reducing oxindol by zinc powder with the aid of heat, 
Baeyer obtained indol, the parent substance of the indigo 
group. 

C«H^NO + Zn = C«H^N -f- ZnO 

Oxindol. Indol. 

^ He has also made the synthesis of indol by heating ortho- 
nitrocinnamic acid with potassium hydroxide and iron filings. 

Orthonitrocinnamic acid. Indol. 

This^ reaction is a proof of the constitution of indol and its 
derivatives. 

Properties. — Indol is a solid, crystallizing in brilliant colorless 
plates. It melts at 52°, and boils with partial decomposition 
WW 62^ 



738 ELEMENTS OF MODERN CHEMISTRY. 

at 245°. Its vapor is carried over by vapor of water. Its 
odor recalls that of naplithylamine. It dissolves readily in 
boiling water and in alcobol and ether. It has feebly basic 
properties. 

Indol is formed normally during the pancreatic digestion by 
the breaking up of albuminoid matters. It occurs, together 
with its methyl derivative, skatol^ in human excrements. 

Skatol, C^H^N, has also been obtained synthetically in 
shining leaflets, having a strong faecal odor, and melting 
at 95°. 



NAPHTHALENE. 

C10H8 

This important compound was discovered by Glarden in 1820, 
in coal-tar. Its composition was determined by Faraday, and 
its properties and transformations were principally studied by 
Laurent. 

It is a frequent product of the dry distillation of organic 
matters, and is formed in abundance when these matters, or 
the products of their decomposition, are heated to high tem- 
peratures. Thus it is formed in large quantities when tar is 
passed through red-hot tubes. 

Naphthalene is extracted from coal-tar, and is purified by 
crystallization in alcohol, or by sublimation. 

Properties. — Naphthalene occurs in rhombic tables when it 
has been sublimed, and is deposited in prisms from its ethereal 
solution. It melts at 79.2°, and boils at 218°. It is inflam- 
mable, and burns with a very smoky flame. It is insoluble 
in water, slightly soluble in cold alcohol, freely soluble in 
boiling alcohol and in ether. 

By its general properties naphthalene is closely related to 
benzene : reagents afi"ect it in a similar manner, and the com- 
pounds which result from the replacement of its hydrogen 
atoms, or the addition of hydrogen or chlorine, are analogous 
to the corresponding benzene derivatives. 

Nitric acid attacks naphthalene, forming nitro-derivatives, 
among which is nitro-naphthalene, C^''H'(NO^), which crystal- 
lizes in sulphur-yellow, rhombic prisms, fusible at 61°. By 
long boiling with dilute nitric acid, naphthalene is converted 
into phthalic acid and carbon dioxide. Nitronaphthalene 
oxidized in the same manner yields nitrophthalic acid. 



NAPHTHALENE. 



739 



By the action of reducing agents nitronaphtlialene is con- 
verted into amidonaphthalene (a-naphthylamine), just as 
aniline results from tlie reduction of nitrobenzene. This 
amidonaphthalene, upon oxidation, gives phthalic acid. 

These facts are readily explained by assuming that the 
naphthalene molecule is formed by two benzene nuclei joined 
together, or condensed, in such a manner that two adjacent 
carbon atoms are common to both (Erlenmeyer), thus, — 



or 



Kekule's formula. 



Centric formula. 



When phthalic acid is produced by the oxidation of naph- 
thalene, one of the nuclei is destroyed, and the two carbon 
atoms which remain attached to the other nucleus become 
oxidized to carboxyl. In nitronaphthalene, under the same 
conditions, the nucleus which does not contain the nitro- 
group is oxidized, while in the case of amidonaphthalene 
the other nucleus, which contains the amido-group (in ex- 
actly the same place as the nitro-group of the former acid), 
is destroyed. 

This view of the constitution of naphthalene derives sup- 
port from various syntheses (see a-naphthol), and satisfac- 
torily accounts for all known cases of isomerism in the naph- 
thalene group. 

According to the positions occupied by the substituting 
atoms or groups, we have two series of mono-derivatives. 
The a-compounds are those which result from the replacement 
of one of the four hydrogen atoms which occupy an ortho- 
position with respect to a carbon atom common to both 
nuclei ; and in the ^-compounds one of the remaining four 
positions is taken by the entering atom or group. 

Numerous isom.ers are known of many of the disubstituted 
naphthalenes. When the substituting atoms or groups are 
identical, ten are theoretically possible, and when the sub- 
stituents are different, as many as fourteen isomers may 
exist. 



740 ELEMENTS OF MODERN CHEMISTRY. 

Chlorine acts on naphthalene in two ways: it combines 
directly, forming chlorides of naphthalene, and produces 
numerous substitution products which generally combine 
with an excess of chlorine. Bromine yields only substitution 
compounds. 

Among all these products, we may mention the following : 
Cioji8Q\2 naphthalene dichloride. C^^'H'^Cl monoehloronaphthalene. 
C10H8C14 naphthalene tetrachloride. CIOH6CI2 dichloronaphthalene. 
C10H6C12C14 dichloronaphthalene tetra- CiORSCls trichloronaphthalene. 

chloride. 
C^OCFCP perchloionaphthalene di- Ci^'CF perchloronaphthalene. 

chloride. 

Concentrated sulphuric acid dissolves naphthalene, forming 
o- and /3-Naphthalenesulphonic acids, Ci^H'^.SG^H 
Naphthalenedisulphonic acids, CioH^ | ^^3^ 

The formation of the first of these acids is expressed in 
the following equation : 

Naphthalene. Naphthalenesulphonic acids. 

NAPHTHOLS. 

CioH'.OH 
These bodies are formed artificially by treating naphtha- 
lene with sulphuric acid, and fusing the naphthalenesulphonic 
acids so obtained with potassium hydrate (see page 678). 

C^'^HISO^K + KOH = K^'SO^ + C^^H^OH 

Potassium naphthalene- Naphthols. 

sulphonate. 

a-Naphthol is formed by heating pheni/lisocrotomc acid * to 
its boiling-point (Fittig and Erdmann). 



CH CH 


CH CH 


^\/\ 


^\/\ 


HC C CH 


HC C CH 


1 II 1 = 


= H20 + 1 11 1 


HC CH CH2 


HC C CH 


\/ / 


\X\^ 


CH CO.OH 


CH C(OH) 



a-Naphthol forms silky needles or laminae, soluble in alco- 
hol, ether, and benzene, almost insoluble in cold water, 
slightly soluble in boiling water. It melts at 94°, and boils 

* This is obtained by the action of benzaldehyde upon succinate of 
sodium in presence of succinic anhydride. 

C6H6.CHO + C0.0H-CH2.CH2.C00H = C6H5-CH=CH-CH2CO.OH + CO2 + H^O 



I 



ANTHRACENE AND PHENANTHRENE. 741 

at 278-280°. Its aqueous solution produces a violet color 
with chloride of lime. When treated with reagents, it forms 
derivatives analogous to those of phenol. 

^-naphihol is prepared from sodium /?-naphthalenesulpho- 
nate. It crystallizes in small rhombic tables, fusible at 122°, 
and boils at 285-290°. 

The mono- and di-sulphonic acids, obtained by heating the 
naphthols with sulphuric acid, are used in the preparation of 
many important coloring matters. Naphthol yellow, for ex- 
ample, is dinitro-a-naphthol sulphonic acid, and /3-naphthol 
orange and rocellin (a substitute for cochineal) are complex, 
derivatives of /S-naphthol. 

NAPHTHYLAMINES. 

C10H9N = C10H7.NH2 

Zinin obtained amidonaphthalene in 1842 by reducing 
nitronaphthalene by ammonium sulphydrate, which may be 
advantageously replaced by iron and acetic acid. 

Nitronaphthalene. Naphthylamine. 

This a-najphthylamine forms fine, colorless needles. It sub- 
limes at a gentle heat, melts at 50°, and boils without alteration 
at 300°. It has a fetid odor. Its reaction is not alkaline, 
although it perfectly neutralizes the acids, with which it 
forms well-defined and crystallizable salts. When exposed 
to the air, the salts of naphthylamine acquire a violet color, 
probably due to an absorption of oxygen. 

^-naphtJiylamine is prepared by heating /?-naphthol with 
ammonia in presence of zinc chloride. It crystallizes in 
pearly needles, fusible at 112°, and boils at 294°. 

The reactions of the naphthylamines are analogous to 
those of aniline. Their diazo- and diazoamido-derivatives 
are applied in the preparation of valuable dyes. 

ANTHEACENE AND PHENANTHRENE. 

Anthracene, which is solid, exists in the less volatile 
products of the distillation of coal-tar. It is obtained from 
the last products of this operation. The mass, which has 
a buttery consistence, is squeezed in a filter-press, and the 



742 ELEMENTS OF MODERN CHEMISTRY. 

residue is submitted to repeated distillations ; it is finally 
purified by compression and several crystallizations in ben- 
zene. 

Anthracene may be formed artificially by several processes. 

1. By passing the vapor of toluene and various derivatives 
of that body through a tube heated to bright redness. Under 
these conditions, two molecules of toluene lose six atoms of 
hydrogen, and are converted into anthracene. 

C6H5-CH3 „„ C6H4=CH 

— 3H2 = I 

C6H5-CH3 C6H4=CH 

2 luol. toluene. Anthracene. 

2. By heating phthalic anhydride with benzene in presence 
of aluminium chloride, orthobenzoylbenzoic acid is obtained ; 
this, upon treatment with phosphorus pentoxide, is converted 
into anthraquinone, which, when reduced with zinc dust, 
yields anthracene. 

In the pure state, anthracene forms monoclinic tabular 
crystals which are colorless, and present a magnificent blue 
fluorescence (Fritzsche). They melt at 213°, and distil with- 
out alteration at 345°. 

By the action of oxidizing agents, such as chromic acid, an- 
thracene is converted into a solid body, which crystallizes in 
beautiful yellow needles, fusible at 276°, and which can be 
sublimed without alteration. It is antliraqiiinone^ C^^PPO^ a 
body which bears the same relations to anthracene as quinone 
to benzene. 

Q6JJ6 QUJJIO 

Benzene. Anthracene. 

Qninone. Anthraquinone. 

The constitution of anthraquinone is expressed by the formula 

By treating anthraquinone with bromine, Graebe and Lieber- 
mann converted it into dibromanthraquinone, C^^H^Br^O'^ a 
solid body, which crystallizes in yellow needles. 

Phenanthrene. — Besides anthracene, there is another hydro- 
carbon of the same composition, which exists in coal-tar, and 
may also be formed artificially. It is called phenanthrene, and 
forms colorless scales, having a bluish fluorescence. It melts 
at 100°, and boils at 340°. It is soluble in 50 parts of alco- 



ALIZARIN. 743 

hol at 13° ; very soluble in hot alcohol, and in ether and 
benzene. 

Its constitution is expressed by the formula 

C«H*— CH 

ALIZAEIN. 

Ci*H804=:Ci*H6(OH)202 

Natural State and Synthesis. — Alizarin is the name ap- 
plied to the coloring matter of madder (Euhia tinctorum) 
which Eobiquet was the first to extract in a pure state. 
Graebe and Liebermann made its synthesis in 1868 by 
heating dibromanthraquinone to 200° with potassium hy- 
droxide. 

C^^H^Br^O^ + 2K0H = 2KBr + Q''W(01iyO'' 

Dibromanthraquinone. Alizarin. 

Alizarin does not exist ready formed in the madder plant. 
The latter contains a glucoside to which Bobiquet has given 
the name ruherythric acid^ and which is decomposed by the 
action of acids into alizarin and glucose. 

(.26JJ28QU _|_ 2W0 = C^'H^O* + 2C«Hi20« 

Euberythric acid. Alizarin. Glucose. 

Preparation. — Alizarin may be extracted from madder by 
boiling the latter with a solution of alum. The filtered liquid, 
left to itself for some days, deposits impure alizarin as a brown- 
red precipitate, and holds in solution another coloring matter 
which is called purpurin. 

The precipitated alizarin is purified by washing with dilute 
hydrochloric acid, and crystallization in alcohol. The product 
thus obtained is exhausted with a boiling solution of alum, 
which removes the purpurin, and is finally dissolved in ether, 
which deposits it in crystals. 

Alizarin is now almost exclusively obtained from anthra- 
cene. This hydrocarbon is oxidized to anthraquinone, and 
the latter body treated with fuming sulphuric acid to con- 
vert it into anthraquinonesulphonic acid. The sodium salt 
of this acid is fused with sodium hydroxide, and a small 
quantity of potassium chlorate is added to the fused mass. 

gi6H7(S03Na)02 4- 3NaOH+02 = C"H6(0]S'a)202+ Na2SO*+2H20 



744 ELEMENTS OF MODERN CHEMISTRY. 

The alkaline mass is dissolved in water, precipitated by 
hydrocliloric acid, and the precipitate purified by crystalliza- 
tion from toluene and finally by sublimation. 

The artificial product is delivered to commerce in the form 
of a paste, but the reaction by which it is formed produces, at 
the same time, isomerides which remain mixed with the aliza- 
rin, properly so called. Eight isomeric compounds are known 
having the composition C^^H^O*. One of them, purpuroxan- 
thin, is contained in small quantity in madder. 

Properties of Alizarin — Alizarin forms long, brilliant, 
orange-yelk w prisms. It is scarcely soluble in cold water, but 
dissolves better in boiling water, and is soluble in alcohol, 
ether, and carbon disulphide. It melts at 278°, and sublimes 
in long, orange-red needles. It dissolves in sulphuric acid 
with a blood-red color, and water precipitates it without alter- 
ation from this solution. Boiling dilute nitric acid converts 
it into oxalic and phthalic acids. When alizarin is heated 
to redness with zinc powder, it is reduced to anthracene 
(G-raebe and Liebermann). 

Alizarin forms combinations with the bases ; it dissolves 
in ammonia, with a purple color, and in the caustic alkalies, 
yielding purple solutions which have a blue reflection. 

Uses. — Alizarin produces a red color (Turkey red) on 
fabrics that are mordanted with alumina, or with ricinoleic- 
sulphonic acid,* and a violet on those which are mordanted 
with ferric oxide, 

PURPUEIN. 

Ci*H5(OH)302 

This name is given to another coloring matter which may be 
extracted from madder, and which has already been mentioned. 
It appears to exist in the plant as a glucoside. It dissolves 
readily in alcohol and ether, with a red color. 

It crystallizes from weak alcohol in orange-colored needles, 
which contain one molecule of water of crystallization. From 
concentrated alcohol, it deposits in red, anhydrous needles. 
When heated, it melts at 254°, and sublimes in red needles. 
With aluminium mordants, it gives scarlet-red shades. 

Purpurin is an oxyalizarin, or a trioxyanthraquinone, 
C^*H^(OH)^0^ : indeed, it may be obtained by treating a 

* This is prepared by treating castor oil with sulphuric acid.. 



FURPURANE, THIOPHENE, AND PYRROL. 745 

solution of alizarin in concentrated sulphuric acid with an 
oxidizing agent, such as manganese dioxide (de Lalande). 
Inversely, the reduction of purpurin reproduces alizarin 
(Rosenstiehl). It undergoes a complete reduction, and is 
converted into anthracene, when heated with zinc-dust. 

Anthrapurpurin and JiavopiLrpurin are isomeric with the 
purpurin just described ; they are contained in commercial 
alizarin. 



The hydrocarbons of the aromatic series and the products 
obtained from them by substitution and addition all contain 
closed chains consisting of carbon atoms exclusively. There 
exist, however, very numerous compounds of an " aromatic 
character" whose nuclei are not made up entirely of carbon 
atoms, but in which other elementary atoms, such as oxygen, 
sulphur, and nitrogen, form part of the closed chains. 

Among these bodies we will consider furfurane, thiophene, 
pyrrol, pyridine, and quinoline, and some of their more im- 
portant derivatives. 

FURFURANE, THIOPHENE, AND PYRROL. 

When the barium salt of pyromucic acid (page 662) is 
heated with a little soda-lime, a colorless liquid of peculiar 
odiOY^ furfurane^ C*H*0, distils. 

Thiophene^ C*H*S, and pyrro?, C*H^NH, are similar bodies 
which occur in small quantities in coal-tar. 

The striking analogies in the chemical behavior of these 
bodies, as well as their close resemblance to benzene, are best 
accounted for in the formulae 

HC — CH HC — CH HC — CH 

„ll II II II II II 

HC CH HC CH HC CH 



Y 



NH 

Furfurane. Thiophene. Pyrrol. 

Furfarane is contained in pine-tar. It boils at 32°, is 
insoluble in water, but miscible with alcohol and ether. 

Its most important derivative \b furfural, C*H^O-CHO, an 
aldehyde. This is formed in the dry distillation of many 
carbohydrates, and most readily by heating bran or sawdust 
2a 63 



I 



746 ELEMENTS OF MODERN CHEMISTRY. 

with dilute sulphuric acid. Furfurol is a colorless liquid of 
peculiar odor. It boils at 162°. When heated with silver ox- 
ide and water it is oxidized to pyi'omucic acid, C*H^O.COOH, 
which also results from the dry distillation of mucic acid. 

Pyromucic acid crystallizes in colorless leaflets, melting at 
134°. Treated with bromine and water, it is converted into 
fumaric acid, carbon dioxide being given off. 

Thiophene was discovered by Y. Meyer in commercial 
benzene. Its isolation from this source offers considerable 
difficulty, but a very pure product may be obtained syntheti- 
cally by heating a mixture of dry sodium succinate and phos- 
phorus trisulphide (Volhard and Erdmann). 

The physical as well as the chemical properties of thio- 
phene are remarkably like those of benzene. It is a colorless, 
mobile liquid, which congeals at very low temperatures. Its 
boiling-point is at 84°. The derivatives of thiophene are 
made in the same manner as those of benzene, which they 
closely resemble in their properties. 

Of the homologues of thiophene, thiotolene, C^H^S.CH^, 
and thioxene, C*H^S(CH^)^, occur in coal-tar. Having nearly 
the same boiling-points as the corresponding benzene deriva- 
tives, they accumulate in the fractions constituting commer- 
cial toluene and xylene. 

TMophfene, C^H*S^, may be regarded as the " naphtha- 
lene" of the thiophene group. Its constitution is expressed 
by the formula 
^ C 

HCn n nCH 

HC\ jL /CH 

s s 

MtrotMophene, C*H^S.NO^ is one of the products of the 
action of nitric acid upon thiophene. It is a solid, crystal- 
lizing in monoclinic prisms, and melting at 44°. It boils at 
224°. Upon reduction with tin and alcoholic hydrochloric 
acid, it yields amidotUophene, C^H^S.NH^ The free base, 
which is a colorless oil, is very unstable. It is not diazotized 
by treatment with nitrous acid, but it forms azo-compounds 
with diazo-derivatives of benzene. 

TMophenesidplionic add, C'H^S.SO^H, is easily obtained 
by the direct sulphonation of thiophene : by repeated treat- 
ment with sulphuric acid, commercial benzene may be de- 



PYRIDINE AND ITS DERIVATIVES. 747 

prived of the admixed tliiopliene. When superheated with 
water, the sulphonic acid is resolved into thiophene and sul- 
phuric acid. 

The very numerous derivatives of thiophene that have 
been described by V. Meyer and others also include phenols, 
aldehydes, ketones, carboxylic acids, etc. 

The " indophenin" reaction, which has already been given 
(page 736), constitutes the most delicate test for thiophene. 

Pyrrol was discovered by Runge. It is present in coal- 
tar and in bone-oil, and is produced in the dry distillation 
of ammonium mucate. When freshly prepared it is a color- 
less liquid, which turns brown in the air. It boils at 131°. 
Although practically insoluble in water, it mixes readily with 
alcohol and ether. Metallic potassium converts it into potas- 
sium-pyrrol, C*H*(NK), a crystalline body which is decom- 
posed by water into pyrrol and potassium hydroxide. When 
treated with nascent hydrogen, pyrrol is reduced to pyrroline^ 
C*H^(NH), a strong base, boiling at 91°. By heating this 
base with hydriodic acid, it takes up more hydrogen and is 
converted into pyrrolidine, C*H^(NH), an alkaline liquid 
which boils at 83°. 

The most characteristic test for pyrrol consists in exposing 
to its vapor a pine shaving moistened with hydrochloric acid : 
it assumes a deep-red color. 

A great variety of substitution products of pyrrol have been 
obtained. Both the hydrogen of the imido-group and that 
united with the carbon atoms may be replaced by alkyl groups. 

lodol (tetraiodopyrrol), C*P(NH), is an odorless substitute 
for iodoform. It is made by the action of iodine and an 
alkali upon pyrrol. It crystallizes in yellow leaflets, soluble 
in alcohol. 

PYRIDINE AND ITS DEBIVATIYES. 

From the oil obtained by the dry distillation of animal mat- 
ters, and which was formerly known as the hone oil of Dip- 
•pel, Anderson has extracted a series of bases isomeric with 
the aromatic amines. Among these bases are the following : 

Pyridine, C^HSN. 

Picolines, C^H'^N, isomeric with aniline. 
Lutidines, C^H^N, isomeric with toluidine. 
Collidines, C^HUN, isomeric with xylidines. 
Parvolines, C»Hi3N, etc. 



•748 ELEMENTS OF MODERN CHEMISTRY. 

These bases also occur in coal-tar ; in fact, they are gen- 
erally formed when nitrogenous organic matter is subjected 
to destructive distillation. 

Some of the bases, as well as many of their derivatives, 
have been obtained synthetically. The following are the 
most important modes of formation that have been observed : 

1. Pyridine is produced when a mixture of acetylene and 
hydrocyanic acid is passed through a red-hot porcelain tube. 

2C'H2 + HCN =r C^H^N 

2. By the action of ammonia upon certain aldehydes, oxi- 
dized bases are formed, thus : 

Acrolein. Acrolein-ammonia. 

2C^H60 + NH^ = C'H^^NO + H^'O 

Crotonaldehyde. 

By dehydration these condensation products yield pyridic 

Picoline, 
CoUidine. 

3. Baeyer and Ador have also obtained a collidine (alde- 
iiydine) by heating aldehyde-ammonia in closed vessels. 

Collidine, 

4. Pyridine is formed by the action of methylene iodide 
and sodium methylate upon potassium pyrrol. 

5. Piperidine (hexahydropyridine) results when penta- 
methylene hydrochloride is rapidly heated. 

C^Hi«(NHOlHCl = (JWm + NmCl 

This base yields pyridine when heated with concentrated 
sulphuric acid. 

6. A dihydro-dicarboxylic acid of collidine is obtained 
when aldehyde-ammonia is heated with acetoacetic ether. 
2C6H10O3 + CH3.CH0 + ^W = C5N(H2)(CH3)3(CO.OH)2 -f BWO 

The two additive hydrogen atoms are removed by treat- 
ment with nitrous acid. 

The first term of the series is pyridine. . According to an 
ingenious hypothesis of Kbrner, this compound has a consti- 



PYRIDINE. Y49 

tution analogous to that of benzene, tlie five carbon atoms 
and the nitrogen atom forming a closed chain similar to the 
benzene nucleus. 

H H 

c c 



HC CH HC CH 

I II I II 

HC CH HC CH 

^^ V 

C N 

H 
Benzene. Pyridine. 

The higher homologues of pyridine, such as picoline, luti- 
dine, and collidine, then result from the substitution of one 
or more methyl or other alkyl groups for the hydrogen of 
pyridine. According to the position of these groups with 
relation to the nitrogen atom in the pyridic chain, isomerism 
will occur, precisely analogous to that which we have con- 
sidered in the case of the aromatic amines. 

Pyridine may, indeed, be regarded as a mono-substituted 
benzene, its nitrogen occupying the place of a CH group. 
The mono-derivatives of pyridine are therefore analogous 
to the di-derivatives of benzene. They exist in three isomeric 
forms, designated as a-, /5-, and ^-derivatives, and correspond- 
ing to the ortho-, meta-, and para-disubstituted benzenes. 

We cannot extend these theoretical considerations. How- 
ever, the pyridic bases and quinoline, which is related to 
them, appear to take part in the constitution of the natural 
alkaloids. Indeed, some of the latter, such as cinchonine 
and brucine, yield by distillation with potassium hydrate a 
mixture of pyridic bases and quinoline. 

Pyridine, C^H^N. — This base has been obtained from the 
animal oil of Dippel by Anderson, and from coal-tar by 
Greville Williams. 

It may be prepared from these products, but is best ob- 
tained in a pure condition by heating nicotinic acid (see 
page 750) with lime. 

C^H^N.COOH == C^ffN + CO^ 

It is a colorless liquid, having a characteristic odor, and at 
0° a density 1.003. It boils at 115°, and is soluble in water 
and alcohol. It is an energetic base, forming deliquescent salts. 
Sodium converts it into a polymeride, dipyridine^ Q^^W^W. 

63* 



750 ELEMENTS OF MODERN CHEMISTRY. 

Piperidine^ or hexahydropyridine, C^H^^N, is formed by 
the action of sodium upon a hot alcoholic solution of pyridine. 

It is a colorless liquid, whose odor suggests that of pepper. 
It boils at 106°, and is miscible with water and alcohol. 

Piperidine is a powerful base which forms crystalline salts 
with acids. 



We cannot describe the other pyridic bases : they all exist 
in several isomeric modifications. Thus, there are three pico- 
lines, or methyl-pyridines, C^H*(CH^)N ; nine lutidines, of 
which six are dimethyl-pyridines and the others ethyl 
derivatives. The collidines comprise trimethyl-pyridines, 
methylethyl-pyridines (aldehydine), and propyl-pyridines. 

Under the action of oxidizing agents, such as potassium 
permanganate in alkaline solution, the pyridic bases behave 
like aromatic hydrocarbons. The lateral chains are oxidized 
and converted into carboxyl, CO. OH. Thus methylpyridine 
(/5-picoline) and ethylpyridine (/?-lutidine) yield the same 
pyridine-carhoxylic (nicotinic) acid, 

C5H*<^^' and C5H*<^'^' yield C5H*<^^-^^ 

Methylpyridine. Ethylpyridine. Nicotinic acid. 

Picolinic add and isonicotinic acid are the corresponding 
a- and ^-derivatives. 

There are ^\x pyridine-dicarhoxylic acids. 

/CO.OH 
C^H^^CO.OH 



QUINOLINE. 

Gerhardt obtained this base by distilling certain natural 
alkaloids, among which are quinine and cinchonine, with 
potassium hydroxide. It is identical with a base which Runge 
had extracted, several years previous, from coal-tar, and which 
he named leacol or leucoline. 

Considerable quantities of quinoline are found in bone-oil. 
Being accompanied by isomeric and homologous bases (iso- 
quinoline, quinaldine, lepidine, etc.), the pure substance can- 



QTIINOLINE, ETC. 751 

not readily be isolated from any of these sources. It may, 
however, be prepared synthetically by a method which was 
discovered by Skraup, and which consists in heating aniline 
with glycerol and sulphuric acid in presence of nitrobenzene. 

Aniline. Glycerol. Quinoline. 

The sulphuric acid aids the condensation by its dehy- 
drating action, and the nitrobenzene plays the part of an 
oxidizing agent. 

Quinoline is a mobile, colorless, strongly refracting liquid. 
Its density at 0° is 1.081, and it boils at 238°. It has a pene- 
trating odor and a very bitter taste. It is insoluble in water ; 
with acids it forms well-defined salts, and behaves as a ter- 
tiary base. With ethyl-iodide it forms quinoline ethiodide. 

C»H'N<^,jj, 

Quinoline is related to the true aromatic compounds, and 
at the same time to the pyridic bases. Its synthetical forma- 
tion and its reactions have led to the following representation 
of its constitution, which is that of naphthalene, in which 
a group CH is replaced by an atom of nitrogen. 

H H 

C C 

^\/\ 
HC C CH 

I II I 
HC C CH 

C N 
H 

Quinaldine, or a-methylquinoline, C^H^(CH^)N, is present 
in coal-tar, and is formed when aniline is heated with paral- 
dehyde and hydrochloric acid (Doebner and Miller). 

It is a colorless liquid, boiling at 246°. 

Besides quinaldine, there exist six mono-methylquinolines 
and many higher homologues. 

Isoquinoline is very similar to its isomeride, quinoline. It 
is present in coal-tar, and has been obtained synthetically. 

It is a solid, melting at 22°. Its boiling-point is the same 
as that of quinoline. 



752 ELEMENTS OF MODERN CHEMISTRY. 

When oxidized witli potassium permanganate it yields cin- 
chomeronic and phtlialic acids. The former is one of the 
pyridine dicarboxylic acids ; its carboxyl groups are in the 
/?- and /'-positions. Hence the constitution of isoquinoline 
must be 



H 


H 


C 


C 


J 


/\ 


1 


II 1 


HC 


C N 


%/\// 


C 


C 


H 


H 



Acridine, C^^H^N, is another solid base contained in coal- 
tar. It accompanies anthracene, from which it may be sepa- 
rated by treatment with sulphuric acid. 

It crystallizes in colorless needles, fusible at 110°, but sub- 
liming even below this temperature. It boils at 360°. It 
forms salts, which in dilute solutions exhibit a blue fluores- 
cence. 

The constitution of acridine is expressed by the formula 

H H 

C C 

^\ H /\ 

HC C— C— C CH 

I II I II I 
HC C— N— C CH 

V Y 

H H 



ALKALOIDS. 

This term has been applied to the nitrogenous organic 
bases which are derived from plants. Many of these sub- 
stances are possessed of poisonous or medicinal properties ; 
they constitute the " active principles" of vegetable drugs. 

The alkaloids cannot be said to represent a sharply-defined 
group of compounds. While the constitution of only a small 
number of these complex bodies is clearly established, it is 
well known that the great majority are derivatives of pyri- 
dine, quinoline, and isoquinoline, others are closely related 



CONINE. 753 

to uric acid, and still others belong to different groups of the 
fatty and aromatic series. 

It is customary to divide the alkaloids into two classes, the 
first of which includes the liquid and volatile bases, the second 
those which are solid. The latter generally contain oxygen, 
the former do not. 

With few exceptions the alkaloids are very sparingly solu- 
ble in water ; most of them, however, dissolve readily in 
alcohol, ether, chloroform, benzene, etc., and they all form 
soluble salts with acids. 

A number of special reagents are used to isolate and identify 
the alkaloids. Platinic and auric chlorides form well-defined 
crystalline double salts (chloroplatinates and chloraurates) 
with their hydrochlorides, and tannic acid, phosphomolybdic 
acid, potassium mercuric iodide, etc., produce precipitates in 
their solutions. From these insoluble compounds the alkaloids 
can be reo;enerated with the aid of alkalies. 



CONINE. 

C8H1W 

This is a liquid and volatile alkaloid which is extracted from 
the hemlock ( Conhim maculatuin). The seeds of this plant are 
crushed and distilled with sodium hydrate. The alkaline liquid 
which collects in the receiver is neutralized by dilute sulphu- 
ric acid, evaporated to a syrupy consistence, and the residue 
exhausted with a mixture of alcohol and ether, which dissolves 
the Conine sulphate, and leaves ammonium sulphate. The alco- 
hol and ether are driven out by evaporation ; a concentrated 
solution of sodium hydrate is added to the conine sulphate, and 
the liquid is distilled. The conine passes with a certain quan- 
tity of water, on which it floats. It is separated, dried over 
some fragments of calcium chloride, and rectified in a 
vacuum. 

Ladenburg made the synthesis of conine by heating a- 
picoline with aldehyde and subjecting the resulting a-allyl- 
pyridine to the action of nascent hydrogen. 

C5H*(CH^)N -f CH«-CHO = H^O + C^HXCH=CH-CH^)N 

a-picoline, a-allylpyridine. 



754 ELEMENTS OF MODERN CHEMISTRY. 

Conine is therefore a-propylpiperidine. 
CH2 



H2C CH2 

I I 
H2C CH-CH2-CH2-CH3 



NH 

It contains one asymmetric carbon atom, and exists in 
three stereoisomeric modifications. Natural conine is dextro- 
rotatory, and the synthetic conine which is inactive can 
readily be broken up into the two active varieties of opposite 
rotatory power. 

Conine is a limpid, oleaginous liquid, having a penetrating 
and nauseating odor, recalling that of hemlock. It boils at 
168°. It is slightly soluble in water, more so in cold than 
in hot water, so that a cold, saturated solution becomes clouded 
when heated. It is very soluble in alcohol and in ether. It 
has a strongly alkaline reaction, immediately restoring the blue 
color to reddened litmus-paper. It precipitates many metallic 
oxides from solutions of their salts. On contact with the air 
it becomes brown and resinified. The density of conine at 0"^ 
is 0.886, 

Conine is often mixed with methylconine, a compound de- 
rived from conine by the substitution of a methyl group for 
an atom of hydrogen, and formed artificially by the action 
of methyl iodide on conine. 

Wertheim has obtained from the flowers and seeds of the 
hemlock a solid alkaloid, which he has named conhydrine, 
C^^H^NO, and which contains the elements of conine plus a 
molecule of water. 

NICOTINE. 

CioHi*N2 

This alkaloid exists in tobacco. It may be obtained by ex- 
hausting tobacco with boiling water and evaporating the liquid 
to a syrupy consistence on a water-bath ; the still hot extract 
is then mixed with twice its volume of alcohol, allowed to settle, 
and the alcoholic liquid separated from the thick lower layer, 
which contains much calcium malate. The alcohol is distilled 
ofi", and the residue exhausted with strong alcohol, of which 
the greater part is then driven off by evaporation. Potassium 



PIPERINE — ATROPINE. TSS 

hydrate is added to the alcoholic extract, which is then agitated 
with ether, which dissolves the nicotine set free. A few grammes 
of oxalic acid added to the ethereal solution causes the separa- 
tion of a syrupy deposit which contains oxalate of nicotine. 
This salt is decomposed by potash and the nicotine set free is 
dissolved out by ether. After the ether has been expelled on 
a water-bath, the nicotine is distilled in a current of hydrogen, 
that part being retained which passes above 180° (Schloesing). 

Properties. — Nicotine is a colorless liquid, having an offen- 
sive, penetrating odor. It rotates the plane of polarization to 
the left. It boils between 240 and 250°, not, however, with- 
out undergoing partial decomposition. Above 146°, it begins 
to distil slowly, and at 100° it emits white vapors ; at ordinary 
temperatures it gives off so much vapor that a rod wet with 
hydrochloric acid will be enveloped in white fumes if held a 
little distance above the nicotine. 

Nicotine dissolves in ail proportions in water, alcohol, and 
ether. It has a strongly alkaline reaction, and perfectly neu- 
tralizes the acids, and precipitates the metallic oxides from 
solutions of their salts. It is one of the most violent poisons 
known. It is a diatomic base ; its chloroplatinate, which 
crystallizes in red prisms, has the composition 

PIPERINE. 

C"Hi9N03 

This alkaloid occurs in various species of pepper, particularly 
in black pepper, from which it may be extracted by alcohol. 
It crystallizes in prisms, fusible at 129°, very soluble in alcohol 
and ether, and insoluble in water. Its reaction is neutral, and 
its salts are not well defined. Sulphuric acid dissolves it, pro- 
ducing a dark-red color. When heated with alcoholic potash, 
it yields piperidine (p. 750) snad piperic acid. 

Piperidine. Piperic acid. 

ATROPINE. 

This alkaloid, which is largely used in the treatment of dis- 
eases of the eyes, was discovered in 1833 by Geiger and Hesse, 
and by Mein, in the deadly nightshade (^Atropa Belladonna). 



756 ELEMENTS OF MODERN CHEMISTRY. 

It has been obtained also from the thorn-apple {Datura Stra- 
mo7num). 

It appears that atropine does not exist already formed 
in the deadly nightshade, but that it is formed during ex- 
traction from an isomeric alkaloid, hyoscyamine, which, 
together with another alkaloid, hyosdne^ exists naturally in 
the plant. 

Preparation. — Belladonna-root is reduced to powder and 
digested several days with alcohol. The solution is filtered, 
slaked lime, in quantity equal to one-twentieth of the weight of 
root employed, is added, the solution again filtered, and rendered 
slightly acid with sulphuric acid. It is again filtered, and | of 
the alcohol distilled oiF. The residue is concentrated at a gentle 
heat, and a concentrated solution of potassium carbonate is added 
until the liquid, now neutral, begins to be clouded. After a few 
hours, the precipitate is separated by filtration, and potassium 
carbonate is added to the filtrate as long as impure atropine is 
precipitated. The next day, the deposit is collected on a filter, 
pressed, dried, and exhausted with 96 per cent, alcohol. The 
solution is decolorized with animal charcoal, the liquid diluted 
with six times its volume of water and put in a cool, dark 
place. The atropine is deposited in twenty-four hours in 
crystalline needles. 

Properties. — Atropine crystallizes in delicate needles, fusi- 
ble at 115°. It dissolves in 300 parts of cold water, and in 
almost all proportions of alcohol. It is less soluble in ether. 
At 140° it volatilizes, but the greater part of it is decomposed. 

In burning, atropine diffuses the odor of benzoic acid. When 
it is treated with potassium dichromate and sulphuric acid, 
benzyl aldehyde distils and benzoic acid is formed (Pfeifier). 

Atropine is a virulent poison. The sulphate of atropiue 
is much used in ophthalmic surgery. A single drop, even of 
a very dilute solution of this salt, produces dilatation of the 
pupil. 

When a small quantity of atropine is moistened with 
nitric acid, evaporated to dryness, and the residue treated 
with alcoholic potash, a rich violet color is developed 
(Vitali). 

A solution of bromine in aqueous hydrobromic acid throws 
down from solutions of atropine a yellow amorphous precipi- 
tate which soon becomes converted into characteristic crystals 
(Wormley). 



COCAINE. 757 

When heated with baryta water, or with hydrochloric acid, 
atropine breaks up into tropine and tropic acid (Lossen and 
Kraut). 

Atropine. Tropic acid. Tropine. 

Tropine is an energetic base, soluble in water, alcohol, and 
ether : from the latter solvent it separates in tables, fusible at 61°, 
It is a derivative of piperidine. 

Tropic acid is the phenyl derivative of hydracrylic acid. 
CH'i.OH CH2.0H 

CH2.C0.0H ^^<CaOH 

Hydracrylic acid. Tropic acid. 

It forms small crystals, fusible at 117°. By long boiling 
with hydrochloric acid, or with baryta water, it loses a molecule 
of water, and is converted into atropic acid, C^H^O^, which 
is isomeric with cinnamic acid. 

CH(C6H5) CH2 

CH C(C«H5) 

CO.OH CO.OH 

Cinnamic acid. Atropic acid. 

Tropic acid and tropine combine, forming a true salt. When 
long heated with dilute hydrochloric acid, this salt loses the 
elements of water, and atropine is formed. 

Tropine tropate. Atropine. 

This partial synthesis of atropine has been effected by 
Ladenburg. 

COCAINE. 

C17H21N04 

Cocaine was obtained by Niemann from coca leaves (^Ery- 
throxylon Coca). It has been studied by Wohler and Lassen. 

Preparation. — Coca leaves are exhausted several times with 
water at a temperature between 60 and 80°, and the solu- 
tion is precipitated by lead acetate, and filtered ; the filtered 
solution is freed from excess of lead acetate by addition of 
sodium sulphate and then, after a new filtration, the solution 
is evaporated. Sodium carbonate is then added until it pro- 
duces a faint alkaline reaction ; the liquid is lastly agitated 
with ether, which takes up the cocaine and leaves it on evapo- 
ration. 

64 



758 ELEMENTS OF MODERN CHEMISTRY. 

Properties. — Cocaine crystallizes in monoclinic prisms 
which are colorless and odorless, and fuse at 98°. It is 
but slightly soluble in cold water, more soluble in alcohol, 
very soluble in ether. Its taste is bitter, its reaction slightly 
alkaline. When heated with hydrochloric acid, it absorbs 
two molecules of water and decomposes into methyl alco- 
hol, benzoic acid, and a crystallizable alkaloid, ecffonine, 

C^H^^NO* + 2H20 = C^H^^NO' + CH*0 + C^H^O^ 

According to Einhorn, ecgonine is a carboxylic acid of 
tropine. 

Cocaine has been made artificially by successively intro- 
ducing the benzoyl and methyl groups into ecgonine. 

It is used in surgery as a local anaesthetic. 

ALKALOIDS OF CINCHONA. 

The different cinchona barks owe their febrifuge virtues to 
several alkaloids, of which the more important, quinine and cin- 
chonine, were discovered by Pelletier and Caventou in 1820. 
Since then, quinidine and cinchonidine have been isolated, the 
first isomeric with quinine, the second with cinchonine. All 
of these are crystallizable alkaloids. When their sulphates are 
heated with sulphuric acid, they are converted into two new 
isomerides, quinicine and cinchonicine. The latter are not crys- 
tallizable. 

Hence the following six alkaloids are known : 

Cinchonine, cinchonidine, cinchonicine . . . Ci^H^ZN^O 
Quinine, quinidine, quinicine C^OH^^N^QZ 

These alkaloids are by no means distributed in the same 
manner in the numerous species and varieties of cinchona bark, 
and these barks are not equally rich in alkaloids. The follow- 
ing summary gives some indications of this difference : 

1 KILOGRAMME OF BARK YIELDS : QTJIMNE SULPHATE. ^^suLPHATE^ 

Yellow ha.r'k (Cinchona Calls ay a) . . 30-32 grammes, 6-8 grammes. 

'Red ha-rk {Cinchona succirubr a) . . . 20-25 " 8 " 

{Loxa (Cinchona condami- 

nea) 8 " 6 " 

HuannGO (Cinchona nitida) 6 " 12 '* 

Quinic Acid. — In the cinchonas, the alkaloids are combined 
with a well-defined, crystallizable acid, whose composition is 
expressed by the formula C^H^^O^. It is quinic acid. 



QUININE. 759 

This acid is obtained from the calcium quinate which is de- 
posited in a few days, when the liquid separated from the quino- 
calcium precipitate is concentrated and allowed to stand (see 
farther on). 

This calcium quinate is purified by several crystallizations, 
and its solution decomposed by oxalic acid. The quinic acid 
remains in the solution, and separates in crystals when the 
liquid is properly concentrated. 

Quinic acid crystallizes in beautiful, transparent, oblique 
rhombic prisms. It is very soluble in water, and but slightly 
soluble in absolute alcohol. It melts at 161.5°, losing at the 
same time the elements of water. 

Its aqueous solution rotates the plane of polarization to the 
left. 

Quinic acid is the benzene addition compound, hexahydro- 
tetrahydroxybenzoic acid, C^HXOH)^CO.OH. When dis- 
tilled with a mixture of sulphuric acid and manganese dioxide, 
it yields quinone, C^H'O'. 

QUININE. 

C20H24N2O2 

When ammonia is added to a solution of sulphate of quinine, 
a white precipitate of quinine is obtained, which, when left to 
itself and moistened with water from time to time, becomes 
ci^stalline by combining with one molecule of water. 

Quinine is very bitter. It dissolves in 2266 parts of cold, 
and in 760 parts of boiling water ; in 1.33 parts of cold alco- 
hol, and 22.6 parts of ether (Regnault). It is also soluble in 
chloroform. Its alcoholic solution turns the plane of polar- 
ization to the left. When water at 32° is added to the hot 
alcoholic solution until a cloud begins to form, resinous quinine 
is deposited, and also colorless, prismatic crystals containing 
three molecules of water. From its ethereal or alcoholic solution, 
quinine crystallizes in delicate silky needles, fusible at 177°. 

Quinine is diacid, that is, each molecule of the base re- 
quires for the formation of saturated salts, two molecules of a 
monobasic or one of a dibasic acid. It is a tertiary base uniting 
directly with the alcoholic iodides to form quaternary iodides. 

auinine Sulphate, 2(C^oH^^N20^).SO*H2 + SH^O—Prep- 
ration. — This salt, which is extensively used in medicine, is 
prepared by boiling yellow bark {GincJiona Calkaya) or red 
bark {^Cinchona succiruhra) with water acidulated with sul- 



760 ELEMENTS OF MODERN CHEMISTRY. 

phuric or hydroctloric acid. A slight excess of milk of lime 
is then added in small quantities to the decoction, and precip- 
itates not only the quinine and cinchonine, but all of the color- 
ing matter (cinchonine red), which forms an insoluble com- 
pound with the lime. The quinic acid remains in solution as 
calcium quinate. The quino-calcium deposit contains also the 
excess of lime, and calcium sulphate, in case sulphuric acid 
has been employed. It is collected on a cloth, allowed to drain, 
pressed, and dried. It is then exhausted with boiling alcohol, 
which dissolves out the alkaloids. 

The alcoholic solution, concentrated by distillation, deposits 
the cinchonine in crystals, in case the bark employed be rich 
in that alkaloid. The mother-liquor retains the quinine. It 
is neutralized by sulphuric acid, and the alcohol distilled off. 
The quinine sulphate crystallizes in a mass on cooling, and is 
purified by redissolving it in boiling water and adding animal 
charcoal. 

It has been proposed to replace the alcohol, in the extrac- 
tion of the quino-calcium deposit, by certain fixed or volatile 
oils, which dissolve quinine. For this purpose, petroleum and 
the heavy oils produced by the distillation of tar, and which are 
abundant in commerce, may be used with advantage. After 
having dissolved the alkaloids in these oils, the solutions are 
agitated with dilute sulphuric acid, which removes from them 
the quinine and cinchonine. Sulphates are thus obtained which 
may be crystallized. 

Properties. — Quinine sulphate occurs in long, thin, light 
needles, which are somewhat flexible. It requires for its solu- 
tion 740 parts of water at 13°, or about 30 parts of boiling 
water. The solution restores the blue color to reddened litmus- 
paper. It turns the plane of polarization to the left (Bouchar- 
dat). When crystallized in alcohol, quinine sulphate contains 
only two molecules of water. 

If some quinine sulphate be suspended in cold water, and a 
few drops of sulphuric acid be added, the sulphate dissolves 
and the liquid acquires a blue fluorescence. 

In this case, quinine sulphate, which is a basic salt, is con- 
verted into a salt, C-oH^'N^OlSO'H^ which has an acid reac- 
tion, and is called quinine acid sulphate. This salt crystallizes 
iu shining needles containing 8 molecules of water : it is 
the normal sulphate. A still more acid sulphate is known, 

g20JJ24JS^2Q2^^gQ4JJ2y ^ ^JJ2Q^ 



CINCHONINE. 761 

If an excess of chlorine-water be added to a solution of 
quinine sulphate, and the liquid be supersaturated with ammo- 
nia, a beautiful green color will be produced. 

This reaction is characteristic of quinine. 

When tincture of iodine is added to a solution of quinine 
sulphate in hot acetic acid, in a few hours the liquid deposits 
large, thin plates. It is iodoquinine sulphate, C^°H^*N^O^Po 
S0*H2 4- 5H^0 (Herapath). 

These crystals appear green by reflected light, and are almost 
colorless by transmitted light. When two of them are crossed, 
the portions which are superposed almost entirely intercept the 
passage of light. In this respect, iodoquinine sulphate acts 
as a polarizer, like tourmaline. 

Uses. — Quinine sulphate is a valuable remedy. It is prin- 
cipally employed as a febrifuge, and generally in the treatment 
of diseases of an intermittent type. It is successfnlly admin- 
istered in other diseases, especially in acute articular rheuma- 
tism, gout, certain neuralgias, etc. 



CINCHONINE. 

Q19H22I^20 

Cinchonine is obtained as an accessory product in the manu- 
facture of quinine. It deposits from its alcoholic solution in 
brilliant, colorless, quadrilateral prisms. It is insoluble in 
water, but soluble in alcohol and chloroform. It is almost 
insoluble in ether, a property which distinguishes it from qui- 
nine. Its alcoholic solution turns the plane of polarization to 
the right. 

Cinchonine has a bitter taste. It melts at 257°, and when 
cautiously heated in the bottom of a closed tube, it partly sub- 
limes in very light, delicate crystals. The salts of cinchonine 
are antipyretics, like those of quinine ; they are, however, 
much less effective than the latter. 

In its chemical structure cinchonine is closely related to 
quinine. 

When distilled with potassium hydroxide, cinchonine yields 
quinoline and a mixture of pyridine bases. 
. Among the oxidation products obtained by the action of 

64* 



762 ELEMENTS OF MODERN CHEMISTRY. 

nitric acid, or, better, potassium permanganate, on cinchonine, 
we may mention two ; they are 

C^H^NO* = C^H^NCCO.OH)'^ 

Cinchomeronic or pyridine dicarboxylic acid. 

C^°H^NO^ = C^H«N(CO.OH) 

Cinchoninic or quinoline-y-carboxylic acid. 

Weidel, who has studied these acids, has also described 
another oxidation product of cinchonine, an acid, C^H^N^O^. 

From the nature of its decomposition products, it is prob- 
able that cinchonine contains a pyridine and a quinoline 
nucleus. 

When oxidized by chromic acid, quinine yields methoxy- 
quinoline-^'-carboxylic acid, which makes it appear probable 
that quinine is methoxycinchonine. 

STRYCHNINE AND BEUCINE. 

Pelletier and Caventou discovered these two alkaloids In 
various vegetable products derived from plants belonging to the 
genus Strychnos, such as nux vomica (seeds of the Strychnos 
Nux vomica), false angustura bark, which comes from the same 
Strychnos, Saint Ignatius bean (seeds of the Strychnos Ignatii), 
etc. These alkaloids appear to be combined in the Strychnos 
with an acid but little known, which Pelletier and Caventou 
called igasuric acid. 

Strychnine, C^^H^^N^O^ — Preparation. — Strychnine is ex- 
tracted from nux vomica by a process analogous to that which 
serves for the preparation of quinine. The crude strychnine 
which deposits in crystals from its alcoholic solution is always 
mixed with brucine. The two alkaloids are separated by con- 
verting them into nitrates, which are made to crystallize ; the 
strychnine nitrate, less soluble than that of brucine, deposits 
in needles, and the concentrated solution afterwards deposits 
voluminous crystals of brucine nitrate. To isolate the alka- 
loids, the corresponding nitrates are precipitated by ammonia, 
and the alkaloid dissolved in boiling alcohol, which deposits it 
in crystals on cooling. 

Properties. — Strychnine crystallizes in rectangular oct^-- 
hedra, sometimes in quadrilateral prisms terminated by foar- 
sided pyramids. It is colorless and odorless, but extremely 
bitter. It is insoluble in water and in ether, and scarcely 
soluble in absolute alcohol. It dissolves readily in ordinary 



ALKALOIDS OF OPIUM. 763 

alcohol, in chloroform, and in the volatile oils. Its alcoholic 
solution turns the plane of polarization to the left. 

When strychnine or one of its salts is moistened with 
strong sulphuric acid, and a little potassium dichromate 
added, a blue color is produced, which changes to violet and 
red, and at last disappears. 

Among the products of the action of fused potassium hy- 
droxide upon strychnine are quinoline, indol, and picoline. 

Strychnine is one of the most active poisons known ; even 
in very small doses it produces violent tetanic spasms. 

Brncine, G^'H^'^N^O' + 4H20.— Brucine, separated from 
strychnine by the process above indicated, crystallizes by slow 
evaporation of its solution in weak alcohol in oblique rhombic 
prisms, which are often quite large. These crystals, which 
contain four molecules of water, rapidly effloresce in the air. 
Brucine is almost insoluble in water, but dissolves readily in 
alcohol and very slightly in ether. The alcoholic solution ro- 
tates the plane of polarization to the left. 

If brucine be moistened with nitric acid, it immediately 
assumes a blood-red color and, by the aid of a gentle heat, 
disengages carbon dioxide and vapors which contain methyl 
nitrite (Strecker). 

When fused with potash, it yields homologues of pyridine. 

ALKALOIDS OF OPIUM. 

Opium is the thickened juice of the capsules of the white 
poppy {Papaver somniferuni) . It is obtained by making in- 
cisions in these capsules from the base to the summit. A milky 
juice exudes, and in the course of a day thickens and solidifies 
in tears. These are removed, pressed together, and fashioned 
into variously-formed masses. 

The basic nature of morphine, one of the crystallizable 
principles of opium, was recognized in 1806 by Serttirner. 
Besides this, opium contains a number of alkaloids combined 
with several acids. Among the latter are sulphuric acid, 
lactic acid, and meconic add, C^H*0^ = C'HO^OH)- 
(COOH)l The latter is one of the more important con- 
stituents of opium ; it possesses the characteristic property 
of producing a blood-red color with ferric salts. Opium con- 
tains also a gummy matter, soluble in water, and a brown, 
insoluble, resinous matter, which remains in the mass when 



764 ELEMENTS OF MODERN CHEMISTRY. 

opium is exhausted with water. The aqueous solution of opium 
has a brown color. The following alkaloids have been obtained 
from opium : 

Morphine Cimi9N03 

Codeine C18H21N03 

Thebaine Ci9H2iN03 

Papaverine C2IH21NO* 

Narcotine C22H23N07 

Nareeine C23H29N09 

Still other alkaloids have been obtained from opium, but 
it is probable that some of them are produced during the 
process of extraction. Of those enumerated, we will describe 
only morphine, codeine, and narcotine. 

MORPHINE. 

CnHi9N03 

Preparation. — 1. Opium is cut into slices and exhausted 
with water. The solution is evaporated to a syrupy consistence 
and the still hot extract is mixed with an excess of pulverized 
sodium carbonate. After the lapse of twenty-four hours, the 
precipitate is collected and exhausted with dilute acetic acid, 
which dissolves the morphine and leaves the narcotine. The 
liquid is filtered, decolorized by animal charcoal, and super- 
saturated with ammonia. The morphine is precipitated, and 
is purified by crystallization in alcohol (Merck). 

2. One kilogramme of opium is exhausted with cold water ; 
100 grammes of pure lime are added to the liquid, which is 
then evaporated to a syrupy consistence at a temperature of 65 
or 75°. After cooling, the mass is exhausted with 3 litres of 
water which leaves the meconate of calcium ; the latter is 
separated by filtration. The liquid is then evaporated to one- 
fourth its volume, and while it is still hot, 50 grammes of 
calcium chloride dissolved in 100 grammes of water and 8 
grammes of hydrochloric acid are added. 

This mixture is left to itself for about two weeks, when it 
will be found to have set in a mass of crystals which are bathed 
in a colored mother-liquor. The deposit is pressed in a cloth, 
dissolved in boiling water, with addition of animal charcoal, 
and the solution filtered. On cooling, a mass of crystals is 
formed, consisting of a mixture of morphine hydrochloride and 
codeine hydrochloride. These are pressed, dissolved in water, 
and ammonia is added, which precipitates the greater portion of 



MORPHINE. 765 

the morplime, while the codeine remains in solution. The 
deposit is collected on a filter and redissolved in boiling alcohol, 
from which the morphine crystallizes on cooling (Robertson 
and Grregory). 

Properties. — Morphine crystallizes in small, colorless, right 
rhombic prisms, having a bitter taste. It is insoluble in ether, 
in chloroform, and in benzene. The alcoholic solution rotates 
the plane of polarization to the left. The crystals contain one 
molecule of water which they lose at 100°. Morphine dis- 
solves easily in solutions of the caustic alkalies, from which 
it is reprecipitated by acids. It is but slightly soluble in 
ammonia ; almost insoluble in water. 

Tests. — 1. If a few drops of a solution of iodic acid be added 
to an alcoholic solution of morphine, the liquid immediately 
assumes a brown or yellow color, due to the liberation of iodine. 
Iodic acid exerts an oxidizing action on morphine. 

2. If a small quantity of morphine powder be added to a solu- 
tion of ferric chloride, a blue color is produced. This charac- 
teristic recalls a reaction of the phenols, and leads to the belief 
that morphine contains a phenolic hydroxyl group (Glrimaux). 

3. Nitric acid produces an orange-red color with morphine. 
The last two reactions are characteristic. 

When morphine is heated to 200° with potassium hydrate, 
it disengages methylamine. 

When heated with zinc dust, it yields phenanthrene, and 
various pyridic and quinolic bases studied by Gerichten and 
Schroetter. 

Morphine Hydrochloride. — This salt, of which the prepara- 
tion has already been indicated, crystallizes in silky needles, 
soluble in 1 part of boiling and 16 or 20 parts of cold water ; 
it is very soluble in alcohol. The crystals contain C^^H^^NO^. 
HCl -f- SH^O. 

Platinic chloride forms a yellow precipitate of a double chlo- 
ride in an aqueous solution of morphine hydrochloride. 
(C"H^9N0^HCl)lPtCl* 

Hydrochloride of morphine is much used in medicine. 

When its solution is heated to 60° with silver nitrite, the 
base is oxidized and converted into oxymorphine, C"H^^NO*. 

When morphine is heated to about 140° with concentrated 
hydrochloric acid, it is transformed into a new base, apomor- 
phme^i C^^H"NO'^, derived from morphine by the removal of 



766 ELEMENTS OF MODERN CHEMISTRY. 

one molecule of water (Matthiessen). This base possesses 
special therapeutic properties. When administered by hypo- 
dermic injection or swallowed, it acts as an emetic. 

CODEINE. 

C18H21N03 

Codeine is methylmorphine. It is obtained from the am- 
moniacal mother-liquor from which the morphine is deposited, 
in the preparation of the latter body by the process of Robert- 
son and Gregory. For this purpose, the mother-liquor is con- 
centrated and caustic potash is added, which precipitates the 
codeine. It is collected, dissolved in hydrochloric acid, the 
solution decolorized with animal charcoal, and the codeine again 
precipitated by potash. Lastly, the precipitate is dissolved in 
ordinary ether, which deposits the codeine in voluminous crys- 
tals by spontaneous evaporation. 

These crystals are right rhombic prisms, and contain one 
molecule of water. Anhydrous ether deposits codeine in anhy- 
drous rectangular octahedra, fusible at 150°. 

Codeine dissolves in 89 parts of water at 15°, and is more 
soluble in boiling water. Alcohol and ether dissolve it readily, 
and the alcoholic solution rotates the plane of polarization to 
the left. 

Starting with the idea that morphine contains a phenolic 
hydroxyl group, Grimaux conceived that the solution of mor- 
phine in potassium hydroxide should contain the compound 
C"H^^NO^.OK : indeed, by treating this alkaline solution with 
methyl iodide, he obtained codeine. 

C"H^«N010K + CH^I = KI + C^H^^NOIOCH' 

This reaction certainly demonstrates that codeine is methyl- 
morphine. 

If bromine-water be poured upon codeine in fine powder, 
the latter dissolves, and is converted into hydrobromide of 
monohromo-codeine. By the continued addition of bromine- 
water, a yellow precipitate is formed, consisting of hydrobro- 
mide of trihromo-cGdeine, that is, codeine in which three atoma 
of hydrogen are replaced by three atoms of bromine. 



NARCOTINE. 767 

NARCOTINE. 

C22H23N07 

Narcotine may be extracted from the residue of opium whicli 
has been exhausted by water. This is treated with hydrochloric 
acid, filtered, and the filtrate precipitated by sodium carbon- 
ate. The precipitate is dissolved in alcohol, and the alcoholic 
solution decolorized by animal charcoal. The narcotine crys- 
tallizes out on cooling. 

It fiDrms brilliant, colorless prisms, belonging to the system of 
the right rhombic prism. It melts at 176°. It is insoluble in 
cold water, and requires for its solution about 60 parts of cold 
absolute alcohol, or 12 parts of boiling absolute alcohol. It is 
soluble in ether, a character which distinguishes it from mor- 
phine. Its alcoholic and ethereal solutions have a bitter taste, 
and turn the plane of polarization to the left. 

If a few crystals of narcotine in a watch-glass be moistened 
with sulphuric acid containing a trace of nitric acid, an intense 
blood-red color is produced. 

By the action of certain oxidizing agents, narcotine is de- 
composed into a new alkaloid, cotarnine, and an acid which is 
called opianic acid (Wohler). 

Narcotine. Opianic acid. Cotarnine. 

Cotarnine crystallizes in colorless, silky needles, grouped in 
stars. They melt at 132°. 

When heated with water, narcotine breaks up into cotarnine 
and meconine, which is also present in opium. 

C22g23JS^'Q7 ^ C'WO' + C^'H^^^NO^ 
Narcotine. Meconine. Cotarnine". 

When subjected to the action of hydriodic acid, narcotine 
loses successively three methyl groups, and yields hydriodides 
of three new bases. One of them contains C^^H^^NO^ and has 
been designated as nornarcotme or normal narcotine. It is 
formed according to the equation 

Q22JJ23^Q7 ^ 3JJJ ^ C^^H^NO' -f- SCH^^I 
Narcotine. Noruarcotine. Methyl iodide. 

Hence narcotine itself represents trimethyl-nornarcotine^ 
(^'m^Xm'f^O'^ (Matthiessen and Foster). 

The intermediate terms between narcotine and nornarcotine 
are also known. 



768 ELEMENTS OE MODERN CHEMISTRY. 

ACONITINE. 

The Aconitum Napellus contains, independently of aconitic 
acid, a base which was extracted by Geiger and Hesse. It 
occurs as a white powder, or as colorless, tabular crystals, only 
slightly soluble in water, very soluble in alcohol. Its taste is 
acrid and bitter. It is a violent poison. Its nitrate crystal- 
tizes readily. 



The following two alkaloids, theobromine and caffeine, are 
not derivatives of the fundamental alkaloidal nuclei ; they 
are closely related to uric acid. 

THEOBROMINE. 

Theobromine exists in the beans of the cocoa (Theohroma 
Cacao). To prepare it, the crushed cocoa beans are exhausted 
with water, and the aqueous extract is precipitated by lead ace- 
tate. The precipitate is separated by filtration, and the filtrate 
is freed from an excess of lead by hydrogen sulphide ; it is then 
again filtered, and evaporated to dryness. The residue is dis- 
solved in absolute alcohol and the solution concentrated ; the 
theobromine separates as a crystalline powder, having a bitter 
taste, slightly soluble in alcohol and ether. It may be sublimed. 
It is soluble in ammonia. 

CAFFEINE, OR THEINE. 

Caffeine was extracted from coffee in 1821 by Pelletier and 
Caventou, and by Robiquet and Runge. Liebig, Pfaff, and 
Wohler determined its composition. It exists in coffee, tea, 
Paraguay tea (leaf of the Ilex Paraguaiensis), guarana (seeds 
of the PaidUnia Sorhilis), and in kola-nuts. Caffeine is 
methyl-theobromine. 

Preparation. — Caffeine, or theine, is generally obtained 
from tea. Powdered tea is exhausted several times with cold 
alcohol, and the tincture is precipitated by subacetate of lead, 
filtered, and a current of hydrogen sulphide passed through 



SUBSTITUTES FOR NATURAL ALKALOIDS. 769 

the filtrate to precipitate the excess of lead. The filtered 
liquid is then evaporated to one-fourth its volume, neutralized 
by potassium hydrate, and allowed to crystallize (Herzog). 

Properties. — CaJBFeine forms long, colorless, silky needles, 
containing one molecule of water. It loses its water of crys- 
tallization at 100°, melts at 225°, and sublimes without alter- 
ation at a higher temperature. It is only slightly soluble in 
cold water, but dissolves readily in boiling water, and in 
alcohol. It is but slightly soluble in ether. It forms definite 
combinations with the acids. When boiled with concentrated 
potash, it disengages methylamine. 

Heated with baryta water, it breaks up into carbon dioxide 
and caffeidine^ C'H^^N'^O, a base soluble in water, and which 
yields by prolonged boiling with water sarcosin and other 
products. 

By the action of chlorine water or of nitric acid, caffeine 
forms methylamine, cyanogen chloride, and an acid, C^^H^^NO', 
which Rochleder has named amalic add. The latter is tetra- 
methyl-alloxantin, C^(CH^)*N*0^ and the reaction indicates 
a relation between caffeine and the uric acid group. 

When caffeine is boiled for a few minutes with fuming nitric 
acid, the yellow liquid evaporated to dryness, and the residue 
moistened with ammonia, a purple color is produced, analogous 
to that of murexide. 

SUBSTITUTES FOB NATUBAL ALKALOIDS. 

Among the more important medicinal properties of several 
of the natural alkaloids are those of relieving pain and of 
lowering the temperature of the body, — the analgesic and 
antipyretic effects. The use of the alkaloids possessing these 
properties in the most marked degree is often objectionable 
on account of other actions on the animal economy. Organic 
chemistry has placed a large number of compounds at the 
service of the physician, and several of these are extensively 
used as substitutes for natural alkaloids. We have space to 
mention only a few. 

Paracetphenetidine, C«H^NH(C^H'0)-OC^H^— The 
ethyl ethers of the amidophenols, e.g., C^H^.NHIOC'H^ are 
called phenetidines, and the acetyl compound formed by the 
replacement of one of the hydrogen atoms of the NH^ group 
in paraphenetidine by the group acetyl is perhaps the most 
2h yy 65 



770 ELEMENTS OP MODERN CHEMISTRY. 

important of the antipyretics. It is a white crystalline pow- 
der, almost insoluble in cold water, more soluble in hot water, 
and freely soluble in alcohol and in ether. It is employed 
in medicine under the nsuRe jpheiiacetin. 

Phenyldimethylpyrazolon, or antipyrine, is a derivative 
of acetoacetic ether. By the reaction of phenylhydrazine 
and ethylacetoacetate, phenylmethylpyrazolon is formed, 
having the composition 

^C0-CH2 
C6H5N< I 

^ N=C-CH3 

If methylphenylhydrazine be substituted for the phenyl- 
hydrazine, phenyldimethylpyrazolon results. 

CO CH 

C6H5N< II 

This is the medicinal antipyrine. It forms monoclinic crys- 
tals, easily soluble in water, alcohol, and chloroform, almost 
insoluble in ether. It melts at 113°, and cannot be distilled 
without decomposition. 

riTi2 r'TT2 

Hydroxymethyltetrahydroquinoline, C6H3.oh< i 

N(CH3j— CH* 
a derivative of orthoamidophenol, has been used as an anti- 
pyretic under the name kairine, and 

C TJ2— PTT^ 

Methoxytetrahydroquinoline, C6H3(och3)< i has 

NH— CH* 

been recommended for the same purpose, being called thalline. 
Neither of these appear to have any advantages over phena- 
cetin and antipyrine, and, moreover, their employment is not 
without danger by reason of special actions they exert on 
certain nerve-centres. 



ALBUMINOID MATTERS-PKOTEIDS. 

The albuminoid matters are complex organic substances, 
containing carbon, hydrogen, oxygen, and nitrogen, associated 
with a small proportion of sulphur. Their composition and 
properties generally are represented by those of the coagu- 
lable matter which exists in white of egg and in the serum 
of blood, and which is called albumen* They are closely 
related to the epidermic productions and insoluble substances 



ALBUMINOID MATTERS. 771 



whicli are converted into gelatin or chondrin by boiling, 
althougb differing from these latter in cbemical composition 
and in many properties. These compounds appear to be the 
closest approximation of unorganized matter to organized 
matter ; that is the living cell, and they have therefore been 
called proteids. 

The following reactions serve to characterize albuminoid 
substances : 

In contact with water containing one or two thousandths 
of hydrochloric acid most insoluble albuminoid matters swell 
up and are finally converted into a transparent jelly, which is 
partially soluble in water. 

Concentrated hydrochloric acid dissolves albuminoid sub- 
stances by the aid of heat, assuming a deep violet or blue 
color. 

Concentrated nitric acid colors them yellow. 

Albuminoid substances are precipitated from neutral or 
slightly alkaline aqueous solutions by alcohol, tannin, phenol, 
and the salts of heavy metals such as lead, mercury, and 
copper. The copper precipitate is soluble in strong potassium 
hydroxide solution, the liquid assuming a rich violet color. 

A solution of mercuric nitrate in dilute nitric acid is 
colored red when boiled with albuminoid substances (^Millons 
reagent. 

The albuminoid substances are levo-rotatory, the optical 
activity varying in wide limits. 

The insoluble albuminoid bodies, such as coagulated albu- 
men, fibrin, and casein, dissolve by the aid of a gentle heat 
in potassium hydroxide, to which they yield a portion of 
their sulphur. The alkaline liquid, supersaturated with acetic 
acid, precipitates the dissolved matter in flakes. 

The molecular composition of these bodies is very com- 
plex, as will presently be seen when we consider the com- 
pounds into which they can be split up, and their molecular 
weights are consequently very great. Their centesimal com- 
position is comprised within the following limits : 

Carbon 50.0 to 53.5 

Hydrogen 6.6 " 6.9 

Nitrogen 16.8 " 15.6 

Oxygen 26.1 « 22.4 

Sulphur 0.5 " 1.6 

100.0 100.0 



772 ELEMENTS OF MODERN CHEMISTRY. 

Concentrated and boiling solutions of the alkalies decompose 
all albuminoid substances, the principal products of the decom- 
position being carbon dioxide, formic acid, glycocoll^ and its 
homologue leucine, C^H^^NO'^ as well as tyrosine, C^H^^NO^ 
aspartic acid, C^H'^0*, and phenylalanine, C^H*-CH^-HC- 
(NH^)-COOH. The other decomposition products will be 
indicated when treating of albumen. 

f Leucine and tyrosine are also formed when albuminoid sub- 
stances are long boiled with dilute sulphuric acid. At the same 
time, aspartic acid, and glutamic acid, C^H^NO*, which is the 
acid amide of normal pyrotartaric acid, is formed. 

Pyrotartaric acid. Glutamic acid. 

By the action of energetic oxidizing agents, such as chromic 
acid, or manganese dioxide and sulphuric acid, albuminoid 
bodies produce various products of oxidation and decomposi- 
tion, among which we may note particularly : (1), the volatile 
acids of the series, C"H^"0"^ from formic acid to caproic acid 
inclusive ; (2), the corresponding aldehydes ; (3), the nitriles 
(hydrocyanic ethers), propionitrile (ethyl cyanide), and valero- 
nitrile (butyl cyanide) ; (4), benzoic acid and benzalde- 
hyde. 

By subjecting albumen and its analogues to the action of 
an aqueous solution of barium hydrate at a temperature of 140 
or 150°, Schiitzenberger observed that these bodies decompose, 
by hydration, into ammonia, carbon dioxide, oxalic, sulphurous, 
and acetic acids (the latter three bodies in very small propor- 
tion), and into other products, which are mostly crystalliza- 
ble. These products are tyrosine and the acid amides of the 
fatty series C^H^^+^NO^ from amidobutyric acid, C*H^(NH2)0^ 
to amid-oenanthic acid, C^H^^(NH^)0^ inclusive. With these 
products are others which are also crystallizable, but contain 
less hydrogen ; lastly, more highly oxidized amides are formed 
in the same reaction, such as malamic, diamidocitric, aspartic, 
and glutamic acids. 

From these results, it may be inferred that albumen and its 
analogues contain the elements of urea, tyrosine, acid amides 
of the fatty series, and more oxidized amides analogous to as- 
partic acid, all of these bodies being combined together, with 
elimination of water. The presence of a certain proportion of 



ALBUMENS. 773 

a dextriniform body in tlie products of the decomposition of 
albumen permits the supposition that the complex molecule 
of the latter body contains also an amide of cellulose or an 
amylaceous body. 

It can now be understood that an exact chemical classifi- 
cation of the proteids is not yet possible. They may, how- 
ever, be conveniently arranged as follows : 

1. True albumens, soluble in pure water and coagulable 
by heat. Egg albumen and serum albumen are types of this 
variety. There are analogous vegetable albumens. 

2. Globulins, insoluble in water^ but soluble in solutions 
of neutral salts, such as sodium chloride, magnesium sul- 
phate : the solutions are coagulable by heat. Examples are 
vitellin, the albumen of yolk of egg, cryosine, serum globu- 
lin, fibrinogen. There appear to be no exactly correspond- 
ing vegetable substances. 

3. Fibrins, insoluble in water, swell up in solutions of 
neutral salts and in dilute acids ; coagulated by boiling water, 
blood fibrin is the best type, and gluten fihrin is an analogue 
of vegetable origin. 

4. Coagulated albumens, insoluble in water, and only 
slightly swelled by saline solutions and dilute acids. These 
substances are not colored by iodine. 

5. Amyloid, insoluble, colored red, brown, or violet by 
iodine. This substance appears to be a pathological modi- 
fication of albuminoids, and cannot be prepared artificially 
from other varieties. 

6. Acid albumens, insoluble in water, saline solutions 
or alcohol, but dissolved by dilute acids and alkalies : a small 
quantity of calcium carbonate suspended in water prevents 
their solution. 

7. Alkali albumens, very slightly soluble in water, saline 
solutions, and hot alcohol ; soluble in water holding suspended 
calcium carbonate, in which they replace the carbonic acid. 

8. Albumoses, apparently transition products between the 
preceding bodies and the next class ; soluble in dilute solu- 
tions of common salt. 

9. Peptones, very soluble in water, not coagulable by 
heat, and not precipitated by acids or salts. 

10. True proteids, capable of being broken up into an 
albuminoid body with some other substance ; such as hemo- 
globin, oxyhemoglobin, casein, chondrin, nuclein, 

65* 



774 ELEMENTS OF MODERN CHEMISTRY. 

11. Albumoids, insoluble matters, in general not dissolved 
by the digestive juices : these occur in the skin and in the 
strong integuments. 

12. Gelatinoids, soluble in hot water without alteration : 
gelatin is the type. 

13. Spongy matters, such as compose sponge. 

We will briefly consider the more important of these 
bodies. 

TEUE ALBUMENS. 

Soluble albumen exists in solution in white of egg, and in 
other liquids of the animal economy. The coagulable prin- 
ciple of the serum of blood is a liquid analogous to the 
albumen of white of egg, and has been called serin. 

When a filtered solution of white of egg is evaporated at a 
low temperature or in a vacuum, the soluble albumen at length 
dries to a transparent, yellowish mass, having a gummy appear- 
ance. In this state it is not pure ; it remains combined with 
a trace of alkali and mixed with a small quantity of salts. 
When treated with water, it again dissolves. When it is per- 
fectly dry, it may be heated to even 100° without losing all of 
its water. The greater part, if not all, of the salts which exist 
in white of egg with the albumen may be removed by dialysis 
(Graham). 

When a solution of white of egg or of the serum of blood 
is heated, the liquid begins to be clouded at 70°, and coagulates 
at about 73°, sometimes in flakes, sometimes in a white mass, 
according to the concentration of the solution ; heat converts 
albumen into the insoluble variety. 

When white of egg is diluted with eight or nine times its 
volume of water and the carbonic acid gas which is dissolved 
or combined with the albumen is carefully expelled at a low 
temperature, a solution is obtained which is not coagulable by 
heat. The lost property may, however, be restored by passing 
carbon dioxide through the liquid. 

If strong alcohol be added to a solution of albumen, a white 
coagulum of insoluble coagulated albumen is produced. 

Action of Acids on Albumen. — Sulphuric, hydrochloric, 
and nitric acids precipitate albumen in thick flakes, which 
retain a certain quantity of acid ; the latter may be removed 
by prolonged washings with water, the residue constituting 
an add albumen. 



ACTION OF SALTS ON ALBUMEN. 775 

The action of nitric acid upon albumen is often used for the 
detection of that substance in pathological urine. A still more 
sensitive reagent is metaphosphoric acid, which precipitates the 
smallest traces of albumen contained in a solution. 

Ordinary phosphoric acid, acetic acid, and lactic acid, do not 
precipitate solutions of albumen. 

Action of Alkalies on Albumen. — When white of egg is 
beaten up with a few drops of a very concentrated solution of 
potassium hydrate, it sets in a few minutes in a soft, trans- 
parent, semi-solid mass, from which the excess of potash may 
be removed by washing with cold water. The residue is albu- 
minate of potash, from which all of the excess of potash may 
be removed by prolonged washings. The gelatinous albumi- 
nate of potash dissolves in boiling water. Acetic acid precipi- 
tates from the solution an alkali albumen , which may be freed 
from salts by dialysis. 

Coagulated albumen dissolves in the alkalies and alkaline 
carbonates, forming albuminates. 

Albumen combines with calcium hydrate, as with potassa ; 
a mixture of white of egg and slaked lime constitutes a very 
hard cement. 

Action of the Salts on Albumen. — Many salts precipitate 
solutions of albumen. Acetate and subacetate of lead form 
dense precipitates of albuminate of lead. Cupric sulphate 
produces a blue precipitate. Corrosive sublimate yields a 
white precipitate, even in very dilute solutions of albumen. 
The insolubility of this precipitate explains the use of albu- 
men as an antidote to corrosive sublimate. 

Solutions of albumen are not precipitated by solutions of 
sodium chloride or sodium sulphate, but when acetic acid is 
added to the mixture a precipitate forms. Reciprocally, a 
solution of albumen to which acetic acid has been added is 
precipitated by solutions of sodium chloride and sodium 
sulphate (Panum). In this case an a.cid albumen is formed. 

In general, the properties of ovalbumen and those of serum 
albumen are very similar ; the latter, however, resists the 
action of acids much more than the former, while it is more 
readily modified by the action of alkalies. 



176 ELEMENTS OF MODERN CHEMISTRY. 



GLOBULIN— FIBRIN. 

Berzelius gave the name globulin to the coagulable albu- 
minoid that can be obtained from red blood-corpuscles, and 
which is probably a decomposition product of hemoglobin. 
It resembles albumen in many properties, but coagulates 
completely only at 93°. It is not precipitated by either 
acetic acid or by alkalies, but is thrown down when a current 
of carbon dioxide is passed through its solution. 

When recently-drawn blood is left to itself, it coagulates 
spontaneously in a few minutes, and soon separates into a 
yellow liquid called the serum^ and a red coagulum, which is 
the clot. The clot contains the red corpuscles, imprisoned in 
an insoluble albuminoid matter. This matter is fibrin ; it is 
formed by the reaction of two globulins which exist in solu- 
tion in the liquid portion of blood, which is called plasma. 
One of these substances is called fibrinogen^ the other is 
serum globulin, sometimes called fibrinoplastin ., or paraglob- 
ulin. These two bodies have been isolated : when they are 
mixed in presence of water and a certain proportion of 
sodium chloride, the whole dissolves at first and the liquid 
soon coagulates spontaneously ; the coagulum is fibrin (Hoppe- 
Seyler). 

Fibrin may be obtained in fibrous masses by beating fresh 
blood. The latter does not coagulate in this case, but the 
coagulable constituent attaches itself in red flakes to the rods 
with which the blood is agitated. By washing these flakes 
in running water, they are freed from the adhering red cor- 
puscles, and obtained in white or grayish elastic masses of a 
fibrous appearance. This substance is entirely insoluble in 
pure water, but dissolves in slightly alkaline solutions, and, 
by the aid of a gentle heat^ even in solutions of certain salts 
which have an alkaline reaction. It decomposes hydrogen 
dioxide into oxygen and water. 

When left to itself during the heat of summer, it putrefies 
very rapidly, and is converted into a blackish liquid, which 
contains albumen. Leucine, and butyric and valeric acids 
are formed at the time. 

When treated with concentrated hydrochloric acid, fibrin 
dissolves, forming a blue solution. When still moist fibrin is 
introduced into water containing one or two thousandths of 



ACID ALBUMENS — SYNTONIN. 777 

concentrated hydrochloric acid, it swells and becomes trans- 
parent, forming a jelly. After some time it dissolves in the 
liquid, although with difficulty, and the solution then contains 
an acid albumen^ syntonin. 

Dilute sodium chloride solutions dissolve fibrin. When 
such a solution is dialyzed, most of the salt passes into the 
exterior liquid, and there remains in the dialyzer a limpid 
solution of the two globulins, coagulable by heat, and pre- 
senting many of the properties of egg albumen (A. Gautier). 

Myosin. — Kiihne designated by this name the albuminoid 
matter existing in solution in the sheaths of the muscular 
fibres (sarcolemma), and which has the property of coagu- 
lating spontaneously after death, thus producing cadaveric 
rigidity. 

Myosin is insoluble in water as well as in a saturated solu- 
tion of common salt, but it dissolves in a solution containing 
ten per cent, of salt. It may be extracted from the muscles 
by the following process : the flesh is chopped up, and decolor- 
ized by washing with water ; it is then triturated with pul- 
verized common salt, and enough water is added to produce a 
10 per cent, solution of salt. After digestion for a few hours 
in the cold, the liquid is filtered and brought into contact with 
rock salt ; as the latter dissolves, it precipitates the myosin in 
flakes. 

Recently-precipitated myosin dissolves in a ten per cent, 
solution of salt, but it loses this property by desiccation. Very 
dilute hydrochloric acid dissolves it, and soon transforms it 
into syntonin. 

ACID ALBUMENS— SYNTONIN. 

Syntonin is the type of acid albumens : it may be prepared 
from muscular tissue. The latter is hashed, washed with 
water, and suspended in a large quantity of water containing 
one-thousandth of hydrochloric acid. The particles of meat 
swell and dissolve abundantly in the liquid, which is then 
pressed through a cloth, filtered, and exactly neutralized with 
sodium carbonate. The syntonin is precipitated in gelatinous, 
colorless flakes, which collect and dry upon the filter in elastic 
films. 

Syntonin dissolves in water slightly acidulated with hydro- 
chloric acid. It also dissolves in lime-water, and in a one 
per cent, solution of sodium carbonate, 



778 ELEMENTS OF MODERN CHEMISTRY. 



PEPTONES— PEPSIN. 

The gastric juice contains a ferment called pepsin^ which 
is capable under certain conditions of profoundly modifying 
all the proteids. The change appears to be an hydrolysis, 
and by it the albuminoids are rendered soluble in water ; the 
solutions are dialyzable and non-coagulable by heat ; they 
are converted into peptones. In this condition they are ready 
for absorption into the animal system. Pepsin displays its 
greatest activity at about 35°, and in dilute hydrochloric acid 
solution ; a given quantity of the ferment is capable of pep- 
tonizing an apparently unlimited quantity of albumen, pro- 
vided the peptone formed be removed from the liquid as 
rapidly as it is produced. Whether the peptones are as 
numerous as the albuminoids from which they are derived 
is as yet undecided ; it is certain, however, that there are 
several varieties, and that after absorption into the body they 
again become true albuminoids. 

The pancreatic juice contains a ferment similar to pepsin, 
called trypsin. 



TRUE PROTEIDS— HEMOaLOBIN. 

This name is given to the crystalline matter which may be 
extracted from red blood-corpuscles, and which was first called 
hematocrystalline. 

Preparation. — Clotted blood is broken up and triturated 
with its own volume of water until it is entirely reduced. It 
is then passed through a cloth, and the liquid is frozen, or 
agitated with small quantities of ether until the corpuscles are 
dissolved. The thawed liquid, or that which has been treated 
with eth'er, deposits a coagulum which imprisons all of the 
unbroken corpuscles. The liquid is filtered, rendered slightly 
acid by acetic acid, and alcohol is added as long as the pre- 
cipitate first formed continues to dissolve. When cooled to 0° 
for several hours, the red liquid sets in a mass of crystals ; 
these are collected on a filter, pressed, and washed with dilute 
alcohol and water, both at 0°. They are purified by dissolving 
them in water at 40° and evaporating the solution in a vacuum, 
or by adding alcohol and cooling the liquid to 0°» 



HEMOGLOBIN. 779 

Composition. — Hemoglobin so prepared has about the same 
composition as albuminoid bodies, but contains a little iron. 
According to Hoppe-Seyler, its composition is 

Carbon 54.18 

Hydrogen 7.2 

Nitrogen 16.2 

Oxygen 21.5 

Iron 0.42 

Sulphur 0.7 

Properties. — Hemoglobin forms crystals which differ accord- 
ing to the blood from which they have been obtained. They 
generally belong to the type 
of the right rhombic prism. 
Those from human blood pre- 
sent, under the microscope, the 
forms indicated in Fig. 136. 
They are red, and doubly re- m 
fracting. They contain water W^^ 
of crystallization. Vn J'|\ 5 ^^ ^ ^ - ., 

They dissolve in water, and I 
more readily in slightly alkaline 
solutions. .^^^if^T^^^--^^A ^ 

The red solution of hemo- 
globin (oxyhemoglobin) has 
an important optical property. ^"^ /^ 
When light which has trav- 
ersed a dilute solution of hemo- Fig. 136. 
globin is decomposed by a 

prism, the spectrum so formed shows two black bands (absorp- 
tion bands) between Fraunhofer's lines D and E (Stokes). 

The crystals of hemoglobin contain oxygen which is weakly 
combined, and which may be removed by exposing the crys- 
tals in a vacuum (Hoppe-Seyler). Oxygenated hemoglobin is 
known as oxyhemoglohin^ and hemoglobin deprived of oxygen 
reabsorbs that gas when brought into contact with it. It is 
curious that carbon monoxide will expel the oxygen from hemo- 
globin, at the same time replacing it (CI. Bernard). The com- 
bination of hemoglobin and carbon monoxide is soluble in 
water. 

The solution of oxyhemoglobin yields its oxygen to certain 
reducing agents, such as hydrogen sulphide. Reduced hemo- 
globin gives an absorption spectrum containing one single band. 




780 ELEMENTS OF MODERN CHEMISTRY. 

situated in a position between ttie two absorption-bands of 
oxyhemoglobin. 

Hemoglobin decomposes hydrogen dioxide. It is very un- 
stable, and if the crystals be dried at a temperature above 100° 
they rapidly become altered. The aqueous solution decom- 
poses spontaneously in a few hours at 15°, or temperatures 
above that point. The acids, even the weak ones, favor this 
decomposition, which is manifested by a change of color, the 
fine red tint of the hemoglobin being replaced by a brown. In 
these cases, hemoglobin decomposes into an albuminoid matter 
(globulin), and a ferruginous pigment called hematin. At the 
same time, small quantities of fatty acids are set free (Hoppe- 
Seyler). 

Hematin. — This substance has received different names. 
Lecanu, who first studied it, named it hematosin. When prop- 
erly purified, it forms a blackish-blue, amorphous powder, which 
is quite stable, since it resists a temperature of 180°. It con- 
tains carbon, hydrogen, nitrogen, oxygen, and iron. When 
incinerated, it leaves 12.8 per cent, of oxide of iron. 

It is insoluble in water, alcohol, ether, and chloroform. It 
dissolves in the alkalies, in ammonia, and in the acids, and is 
readily soluble in ammoniacal alcohol and in alcohol containing 
hydrochloric acid. These solutions are reddish-brown. With 
hydrochloric acid, hematin forms a compound which crystallizes 
in rhomboidal laminae ; the crystals are characteristic and may 
be recognized by means of the microscope (hydrochloride of 
hematin). 

Hematoidin. — This body is doubtless a product of the 
decomposition of hemoglobin. Yirchow found it in orange- 
colored crystals in the remains of old hemorrhages of the brain. 
It is also found in blood which has been exposed to air, and in 
extravasated blood in the Grraefian follicles. It may easily be 
obtained from the yellow bodies contained in the ovaries of the 
cow, by triturating them with glass, and digesting for a few 
days with chloroform. After evaporation of the yellow chloro- 
form solution, the residue is treated with ether to dissolve out 
the fat, 

Hematoidin crystallizes in small, orange-red, transparent 
prisms. It is insoluble in water and alcohol, slightly soluble 
in ether ; it is soluble in chloroform, which it colors golden- 
yellow. It presents certain analogies with bilirubin (page 
786). 



CASEIN — GELATIN. 781 

CASEIN. 

When an acid is added to milk, a thick precipitate of 
casein is at once formed. The lactic acid which forms in 
milk by the fermentation of the milk-sugar produces the 
same precipitation. The milk is then said to curdle. 

Casein dissolves in alkaline liquids and even in certain 
alkaline salts, such as carbonate and phosphate of sodium. 
It exists in this state in milk, which is alkaline when fresh. 
When this solution of alkaline albuminate, to which the 
name soluble casein has been given, is evaporated, it becomes 
covered with a pellicle. Acetic acid precipitates it in flakes, 
combining with the alkali. It is also coagulated by the 
gastric juice, by the action of the ferment known as pepsin. 
This ferment exists in rennet which is prepared from the 
fourth stomach of the calf, and which serves to coagulate 
skimmed milk in the preparation of cheese. Indeed, casein, 
more or less altered by putrefaction, is the basis of the different 
kinds of cheese. 

GELATIN. 

The bones contain a cartilaginous substance, which may be 
isolated by dissolving out the mineral salts, which consist of 
calcium carbonate and phosphate, with hydrochloric acid. 
There remains a semi-transparent, elastic substance, which re- 
tains the form of the bone. This substance, which has been 
called ossein, or collagene, is insoluble in cold water, but by 
prolonged boiling, or more rapidly by digestion with water 
heated to a few degrees above 100°, it dissolves and forms a 
solution, which sets in a transparent jelly on cooling. The 
body formed by this transformation dissolves slightly in cold 
water, and abundantly in boiling water, and the hot solution 
forms a jelly on cooling. Hence the name gelatin. 

Other tissues of the animal economy may be converted into 
gelatin by boiling with water. It is so with the cellular tissue, 
the skin, the scales, and swimming-bladder of fishes. The 
swimming-bladder of the sturgeon, known in commerce as fish- 
glue, famishes very pure gelatin by boiling with water. 

The substances which may 'be converted into gelatin possess 
very nearly the same composition as gelatin itself; hence no- 
thing precise is known concerning the nature of the change 
produced in them by the action of boiling water. 

66 



782 ELEMENTS OF MODERN CHEMISTRY. 

Dry gelatin occurs in transparent sheets, which are sonorous, 
and of which the color varies from yellowish to brown, accord- 
ing to their thickness and purity. 

The aqueous solution is precipitated in white flakes by alco- 
hol. The acids do not precipitate it, with the exception of 
tannic acid, with which it forms a thick coagulum, a combina- 
tion of tannin and gelatin. This action of tannin on gelatinous 
matters is applied in the manufacture of leather, which is ob- 
tained by leaving fresh or green skins, previously swelled by 
soaking in water, in contact with tan, that is, coarsely-ground 
oak-bark, which is well known to contain tannin. 

When chlorine-water is added to a solution of gelatin, a 
white cloud is formed which an excess of chlorine converts 
into a white, flocculent precipitate. 

Solutions of gelatin are precipitated by platinic chloride 
and by corrosive sublimate, but not by alum or the salts of lead, 
copper, silver, etc. When boiled with dilute sulphuric acid, 
gelatin is converted into leucine and a substance to which 
Braconnot gave the name sugar of gelatin, and which is gly- 
cocol. 

Chondrin. — When the cartilages of the short ribs are boiled 
for a very long time with water, they dissolve, forming a liquid 
which sets in a jelly on cooling. This gelatinous matter is 
chondrin. It is distinguished from gelatin by the property of 
its aqueous solution to form precipitates with all the acids, and 
with a great number of metallic salts. Alum forms in it an 
abundant, flocculent precipitate. 



The substances which have just been summarily described, 
and others which form the liquids and tissues of the animal 
economy, undergo various transformations in the organism. 
They are derived from the vegetable kingdom, which alone can 
elaborate such complex matters. They pass with the aliments 
into the animal organisms, which assimilate them, and this work 
of assimilation does not profoundly modify the nitrogenized 
matters. But once fixed in the tissues, they do not remain 
there indefinitely, for there is a continual change and renewal 
of the whole economy. They become unfitted for the require- 
ments of life, and disappear in their turn, eliminated by that 
continual oxidation which makes of the body a permanent 



PRODUCTS OF DISASSIMILATION. 783 

hearth of slow combustion. A notable portion of the oxygen 
which enters the lungs at each inhalation penetrates into the 
blood, and is converted in the capillary system and the intrica- 
cies of the tissues into carbon dioxide. This gas, which returns 
to the lungs with the venous blood, is exhaled at each exhala- 
tion. Expired air contains 4 to 5 per cent, of carbon dioxide. 

The carbon dioxide eliminates the greater portion of the 
carbon contained in the organic bodies burned during the phe- 
nomenon of respiration. The hydrogen of these bodies is 
eliminated in the form of water. But what becomes of their 
nitrogen? In man, and a great number of the higher animals, 
it is eliminated in the urea contained in the urine. Such are 
the principal features of this grand function of respiration, the 
source of heat in all animals. 

But how is this slow oxidation which constitutes the object 
of respiration, as first shown by Lavoisier, accomplished ? Are 
the organic matters ready to be oxidized and consumed at once, 
or does the oxidation take place in successive phases, so that 
there are a certain number of intermediate terms between the 
complex products which must disappear and the final products 
of their oxidation ? All facts lead to the adoption of the latter 
conclusion. Indeed, there are found in the tissues and liquids 
of the economy a great number of bodies having compositions 
more or less complex, and which are the products, and, as it 
were, the testimony of a successive simplification, — of disas- 
similation, as it is called. 

But it must not be supposed that all of the reactions which 
take place in the economy are phenomena of oxidation. Be- 
fore being definitely oxidized and rejected from the body, the 
ingested organic matters and those which form our humors and 
tissues, may undergo various transformations and sometimes 
molecular complications. Thus, when benzoic acid is taken 
internally hippuric acid is found in the urine (Wohler and 
Keller). Analysis has shown the presence in the animal 
economy of a multitude of more or less complex organic 
compounds, nitrogenized and non-nitrogenized, having defi- 
nite compositions, and which are the products of varied re- 
actions. Such reactions take place in the blood and in the 
tissues, principally in glandular organs, such as the liver. As 
it would be impossible to consider all of these products of 
disassimilation, we can only briefly notice the more important. 



784 ELEMENTS OF MODERN CHEMISTRY. 

LECITHINE. 

Grobley gave this name to a phosphorized fatty matter lie 
obtained from yolk of egg, and which had been previously 
obtained from brain-tissue by Vauquelin. It exists in the 
brain and in the nerves, and in the seeds of plants. 

Lecithine forms a homogeneous, translucent mass, which, 
as well as all its compounds, is very alterable. It decomposes 
rapidly when the alcoholic solution of its hydrochloride is 
boiled with baryta-water ; oleate and palmitate of barium 
are precipitated, phosphoglycerate of barium is formed, and 
choline remains in solution (Liebreich). 

Strecker represents this interesting decomposition by the 
equation 



C42H84NP09 -f- 3H20 


= C3H9P06 + C5H15N02 + C18H3402 + G^^B.^iQ'^ 


Lecithine. 


Phospho- Choliue. Oleic Palmitic 




glyceric acid. acid. acid. 



Choline is an oxygenized base of which the constitution is 
known. It is hydroxyethyl-trimethylammonium hydroxide. 

The chloride of this base is formed by synthesis by the 
action of ethylene chlorohydrin on trimethylamine (A. Wurtz). 
C2H*|^H ^ ^(.jj3^3^ ^ (C2H4.0H)J^^j 

Hydroxyethj'l-trimethyl- 
ammonium chloride. 

The constitution of lecithine may be represented by the 
formula — 

/O.CiSHsao -) 

C3H5^0.Ci6H'«iO (CH3)3lN.OH 

^O.PO(OH).O.C2H*J 

CHOLESTERIN. 

C26H*40 

This body is largely diffused in the organism. It exists in 
the bile, and is the principal constituent of most biliary cal- 
culi. It is found also in small quantity in the serum of blood, 
in the brain, in yolk of egg, pus, the liquid of hydrocele, etc. 

Its solubility in alcohol and especially in ether, and the 
facility with which it crystallizes from its solutions, permits 



GLYCOCHOLIC ACID. 785 

its easy isolation, and it may readily be prepared by extracting 
biliary calculi with ether, or with boiling alcohol, and allowing 
the solution to evaporate. Cholesterin ordinarily deposits in 
thin and brilliant, rhombic leaflets or needles. It melts at 
145°, and can be distilled, out of contact with air, at 360°. 

It forms neutral compounds with acids, analogous to the 
ethers ; it seems to be a monohydric alcohol. 



The principal organic constituents of the bile are two com- 
plex acids, both nitrogenized, and one of which contains sul- 
phur. These are glycocholic and taurocholic acids. They are 
not contained in the bile of all animals, and are generally ex- 
tracted from that of the ox. They enter into the composition 
of human bile, which contains in addition coloring matters 
of which the most important are bilirubin and biliverdin. We 
will briefly describe these bodies. 

aLYCOCHOLIC ACID. 

026H43]^06 

This body exists in the bile in the form of sodium glycocho- 
late, which salt may be obtained in crystals from ox's bile. 
The latter is decolorized by animal charcoal, filtered, the 
liquid evaporated, and the residue perfectly dried and dissolved 
in absolute alcohol ; the solution is introduced into a flask, and 
ether is cautiously added so that the two liquids may not mix, 
but form two layers. The latter gradually mingle and the 
sodium glycocholate deposits in crystals (Plattner). 

When dilute sulphuric acid is added to a solution of this 
salt, a cloud is formed, and glycocholic acid is soon deposited 
in fine needles. 

This acid is only slightly soluble in water and ether, but dis- 
solves in alcohol. It is dextrogyrate (Hoppe-Seyler). By the 
action of hydrochloric acid, it is decomposed into cliolalic acid 
and glycocoll (Strecker). 

Glycocholic acid. Cbolalic acid. Glycocoll. 

Cholalic Acid deposits from its ethereal solution in color- 
less prisms, containing two_ molecules of water of crystalli- 
zation. 



786 ELEMENTS OF MODERN CHEMISTRY. 



TAUROCHOLIC ACID. 

C26H45NS07 

The sodium salt of this acid remains dissolved in the ethe- 
real solution from which sodium glycocholate has deposited. 
Tt has not yet been obtained crystallized. It is dextrogyrate. 
When boiled with dilute acids, or with alkalies, it breaks up 
into cholalic acid and taurine (Strecker). 

Taurocholic acid. Cholalic acid. Taurine. 

The presence of biliary acids may be detected in a liquid, 
such as urine, by Pettenkofer's reaction : a little powdered 
sugar is dissolved in the liquid, and concentrated sulphuric 
acid is added with continual agitation, carefully avoiding an 
elevation of temperature. The presence of glycocholic or 
taurocholic acid causes the production of a rich purple color. 

BILIARY PIGMENTS. 

Bilirubin, C^^H^^N^O^, exists in human bile and in biliary 
calculi, and may be extracted from the latter. They are 
crushed, and exhausted, first with ether, which removes the 
cholesterin, then with boiling water, and finally with chlo- 
roform. The coloring matter remains in the residue as 
a calcareous combination ; this is decomposed by adding 
hydrochloric acid, evaporating to dryness, and exhausting 
the dried residue with chloroform. After evaporation, the 
chloroform solution leaves a residue which contains, inde- 
pendently of bilirubin, three other biliary pigments which we 
will only mention : biliprasin, bilifuscin, and bilihumin. Alco- 
hol dissolves the bilifuscin from this residue, and the new 
residue is exhausted with chloroform, which takes up the bili- 
rubin, which alcohol precipitates in orange-colored flakes from 
the chloroform solution. 

Bilirubin is obtained in small, dark-red crystals by evapora- 
tion of its solution in chloroform. It is insoluble in water, and 
very slightly soluble in ether and alcohol, but dissolves in chlo- 
roform, benzene, and carbon disulphide. It is very soluble in 
the alkalies, forming an orange-red solution, which becomes 
pure yellow on addition of water, and from which hydrochloric 
acid precipitates bilirubin. The ammoniacal solution of bill- 



BILIARY PIGMENTS. 1&J 

rubin gives precipitates with calcium chloride, barium chlo- 
ride, and lead acetate. 

Biliverdin, C^*^H^«N^O\— When a solution of bilirubin in 
sodium hydrate is agitated with air, it absorbs oxygen and 
becomes green. Hydrochloric acid precipitates biliverdin 
from the solution. 

It is a bright-green powder, insoluble in water, ether, and 
chloroform, but soluble in alcohol. It contains one more 
atom of oxygen than bilirubin. 

We may add that other coloring matters have also been 
derived from bile. They are bilifuscin, C^^H^°N^O^ and 
biliprasin, C^^ff'N^Ol 

Biliary pigments are found in certain pathological urines, 
and may be detected by Gmelin's reaction. The urine is 
placed in a test-glass and strong nitric acid containing nitrous 
acid in solution is carefully added, so that it may not mix 
with but underlie the urine. Richly colored zones appear at 
the union of the two liquids, passing from green to blue, 
violet, and red. The green color is characteristic, the others 
being also produced by albumen and other substances. 

Among the products of disassimilation we may also mention : 

Leucine, C^H^^NO^, which belongs to the homologous series 
of glycocoll, and is found in many organs, especially in the 
pancreas, the salivary glands, the spleen, and the liver (page 
604). 

Tyrosine, C^H^^NO^, a body crystallizing in fine needles, may 
be obtained from the pancreas and the spleen (page 712). 

It is known also that leucine and tyrosine may be obtained 
directly by the action of alkalies upon complex nitrogenized 
matters (page 772). 

Hippuric Acid, C^H^NO^, the origin of which has already 
been indicated (page 707). 

Uric Acid, C^H*N*0^ which exists in small quantity in 
human urine, and which constitutes a large proportion of 
the urine of birds and reptiles (page 624). 

Allantoin, C*H^N*0^, a product of the oxidation of uric 
acid, which Vauquelin and Buniva formerly extracted from 
the amniotic liquor of the cow, and which has also been 
found in the urine of young calves (page 628). 

Various other products are related to uric acid. They are : 

Xanthine, C^HWO^, a yellow matter, which Proust discov- 
ered in certain rare calculi (xanthic calculi), and which has 



788 ELEMENTS OF MODERN CHEMISTRY. 

also been found in small quantity in the muscles, pancreas, 
liver, and urine. 

Adenine, C^H^N^, has been obtained from the tissue of the 
pancreas. It crystallizes in leaflets containing three molecules 
of water of crystallization. When treated with nitrous acid 
it yields hypoxanthine. 

Hypoxanthine or sarcine, C^H*N*0, a white, amorphous 
substance which Scherer obtained from the spleen, and of 
which Strecker has noticed the existence in muscular tissue. 
Hypoxanthine forms a crystallizable combination with hydro- 
chloric acid. 

When hypoxanthine is boiled with nitric acid, it is converted 
into a nitrogenized body. By the action of reducing agents, 
such as ferrous sulphate, this nitrogenized body is converted 
into guanine, C^H^N^O. The latter body was first obtained 
from guano. It has been found in the tissue of the pancreas. 

According to E. Fischer, uric acid, xanthine, hypoxanthine, 
adenine, and guanine, are all derived from the same parent 
substance, to which he has given the r\B,me purine. The com- 
position of this substance is C^H^N*, and it possesses basic as 
well as acid properties. It is quite soluble in water, and melts 
at 217°. Its constitution is 

N=CH N = CH 

II II 

HC C — N^^ or HC C — NH\ 

I II >CH il II ^CH 

N — C — NH/ N — C — N-^^^^ 



MEASUEES OE WEIGHT. 



1 MilligramniG 
1 Centigramme 
1 Decigramme 
1 Gramme 
1 Decagramme 
1 Hectogramme 
1 Kilogramme 



GRAINS. 

0.01543 

0.15432 

1.54323 

15.43234 

154.32349 

1543.23488 

15432.34880 



OUNCES TROY 
= 480 GRAINS. 

0.000032 
0.000321 
0.003215 
0.032150 
0.321507 
3.215072 
32.150726 



POUNDS 
AVOIRDUPOIS. 

0.0000022 
0.0000220 
0.0002204 
0.0022046 
0.0220462 
0.2204621 
2.2046212 



1 Grain 

1 Oz. Troy 

1 Lb. Avoirdupois 



= 0.064799 grammes. 
= 31.103496 " 



0.453495 kilogrammes. 
1 Cubic Centimetre of water at 4° C. weighs 1 gramme. 



To convert Centigrade degrees into Fahrenheit degrees, multiply by 9 and 
divide by 5 ; add 32°. 

To convert Fahrenheit degrees into Centigrade degrees, subtract 32°, then 
multiply by 5 and divide by 9. 



1 Metre = 39.370708 inches. 

1 Centimetre = 0.39370 " 
1 Millimetre = 0.03937 " 



llnch 



2.539954 centimetres. 



MOHS'S SCALE OF HARDNESS. 



1. Talc. 

2. Gypsum. 

3. Calcite. 

4. Fluor spar. 

5. Apatite. 



6. Feldspar. 

7. Quartz. 

8. Topaz. 

9. Corundum. 
10. Diamond. 



789 



INDEX. 



Abstrich, 346. 
Acetal, 555, 583. 
Acetaldoxime, 554. 
Acetamide, 559. 
Acetanilide, 684. 
Acetates, 548. 
Acetic anhyride, 552. 
Acetoacetic ether, 551. 
Acetone, 557. 
Acetonitrile, 492. 
Acetophenone, 707. 
Acetyl chloride, 555. 
Acetylene, 576. 
Acid, 52. 

acetic, 545. 

acetoacetic, 551. 

aconitic, 623. 

acrylic, 529, 566. 

alloxanic, 626. 

amalic, 769. 

amidacetic, 602. 

amidopropionic, 604. 

amidosuccinic, 613. 

anisic, 711. 

anthranilic, 733. 

antimonic, 197. 

arsenic, 192. 

arsenious, 190. 

aspartic, 614. 

atropic, 757. 

barbituric, 627. 

benzenesulphonic, 676. 

benzoic, 705. 

boric, 203. 

bromic, 140. 

butyric, 562. 

campholic, 725. 

camphoric, 728. 

camphoronic, 728. 

caproic, 565. 

carbamic, 477. 

carbolic, 677. 

carbonic, 219. 
in air, 78. 

/cerotic, 528^ 566^ 



Acid, chlorethylsulphonic, 585. 
chloric, 135. 
chlorous, 135. 
cholalic, 785. 
chromic, 412. 
cinchomeronie, 752, 762. 
cinchoninic, 762. 
cinnamic, 731. 
citraconic, 624. 
citric, 621. 
crotonic, 567. 
cyanic, 474. 
cyanuric, 472, 475. 
dextrotartaric, 616. 
dialuric, 627. 
dibromosuccinic, 611. 
dichloracetic, 553. 
digallic, 660. 
dihydroxypropionic, 601, 
dilactic, 599. 
dioxysuccinic, 614. 
ditartaric, 617. 
dithionic, 106, 119. 
elaidic, 567. 
ethylnitrolic, 510. 
ethylphosphinic, 537. 
ethylsulphonic, 512. 
ethylsulphuric, 511. 
formic, 543. 
fumaric, 612. 
fulminic, 495. 
galactonic, 661. 
gallic, 713, 660. 
gluconic, 661. 
glutamic, 772. 
glutaric, 621. 
glyceric, 601. 
glycocholic, 785. 
glycollic, 595. 
glyoxylic, 596. 
gummic, 654. 
hippuric, 707. 
bydantoic, 630. 
hydracrylic, 597, 601. 
hydrazoic, 160. 

791 



792 



INDEX. 



Acid, hydriodic, 142. 
hydrobromic, 138. 
hydrochloric, 126. 
hydrocinnamic, 732. 
hydrocyanic, 465. 
hydrofluoric, 147. 
hydrofluosilicic, 208. 
hydrosulphurous, 106, 110. 
hypobromous, 139. 
hypochlorous, 132. 
hypophosphorus, 181. 
hyposulphuric, 106, 119. 
hyposulphurous, 106, 110. 
indigodisulphonic, 733. 
indigomonosulphonic, 733. 
indigotic, 710. 
iodic, 144. 
lodopropionic, 562. 
isatic, 736. 
isethionic, 584. 
isobutyric, 563. 
isocrotonic, 567. 
isocyanic, 474. 
isonicotonic, 750. 
isophthalic, 916. 
isosuccinic, 612. 
isovaleric, 564. 
itaconic, 624. 
lactic, 597. 
lactobionic, 644. 
lactonic, 661. 
leucic, 605. 
levolactic, 600. 
maleic, 612. 
malic, 612. 
malonic, 609. 
manganic, 406. 
mannonic, 661. 
mannosaccharic, 661. 
margaric, 565. 
meconic, 763. 
melissic, 566. 
mellitic, 665. 
mesaconic, 624. 
mesotartaric, 620. 
mesoxalic, 626. 
mesoxaluric, 627. 
metaboric, 204. 
metagummic, 664. 
metantimonic, 199. 
metaphosphoric, 185. 
metavanadic, 371. 
methylethylacetic, 564. 
methylnitrolic, 494. 
methylparoxy benzoic, 712, 



Acid, methylsuccinic, 621. 
metoxybenzoic, 711. 
molybdic, 414. 
monobromsuccinic, 611. 
monochloroacetic, 551. 
mucic, 644, 661, 
raphthalenedisulphonic, 740. 
naphthalenesulphonic, 740. 
nicotinic, 750. 
niobic, 362. 
nitric, 167. 

in air, 80. 
nitrocinnamic, 731. 
nitrohydrochloric, 170, 
nitrosalicylic, 710. 
nitrotartaric, 617. 
nitrous, 164. 
oleic, 567. 
opianic, 767. 
ortharsenic, 192. 
orthophosphoric, 183. 
orthoxybenzoic, 709. 
oxalic, 605. 
oxamic, 609. 
oxybenzoic, 709-711. 
oxymalonic, 610. 
palmitic, 666. 
parabanic, 629. 
paralactic, 597, 699. 
paratartaric, 619. 
paroxybenzoic, 711. 
pentathionic, 107. 
perbromic, 140. 
perchloric, 136. 
perchromic, 97. 
periodic, 146. 
permanganic, 407. 
persulphuric, 106, 120. 
phenic, 677. 
phenolsulphonic, 682. 
phenylacrylic, 731. 
phenylisocrotonic, 740, 
phenylpropionic, 732. 
phenylsulphuric, 680. 
phloretic, 669. 
phosphoric, 183. 
phosphorous, 182. 
phthalic, 715. 
picolinic, 750. 
picramic, 682. 
picric, 681. 
propionic, 661. 
prussic, 466. 
purpuric, 628. 
pyrantimonic, 199, 



INDEX. 



793 



Acid, pyridine carboxylie, 750. 
pyridine dicarboxylic, 750. 
pyrogallic, 713. 
pyromucic, 662, 746. 
pyrophosphoric, 184. 
pyrosulphuric, 118. 
pyrotartaric, 617, 621. 
pyruvic, 617, 620. 
quinic, 758. 

ricinoleic-sulphonic, 744. 
rosolic, 692. 
ruberythric, 743. 
saccharic, 643, 661. 
saccharinic, 638. 
salicylic, 709. 
silicic, 209. 
stannic, 418. 
stearic, 566. 
succinic, 610. 
sulphindigotic, 733. 
sulphocarbonic, 225. 
sulphovinic, 511. 
sulphuric, 106, 111. 

constitution of, 115. 

fuming, 118. 

test for, 118. 
sulphurous, 106. 
sulphydric, 102. 
tannic, 659. 
tantalic, 372. 
tartaric, 614. 

inactive, 619. 
tartronic, 610, 617. 
taurocholic, 786. 
terephthalic, 716. 
tetraboric, 204. 
tetrathionic, 107. 
thiocyanic, 482. 
thiophenesulphonic, 746. 
thiosulphuric, 106, 119. 
tricarballylic, 623. 
trichloracetic, 552. 
trimethylacetic, 564. 
trithionic, 607. 
tropic, 757. 
tungstic, 415. 
uric, 624. 
valeric, 564. 
Acids, 31, 52. 

diatomic, 461. 
fatty, 541, 559. 

synthesis of, 541. 
ketonic, 620. 
metallic, 257. 
monobasic, 451. 

2i 



Acids, polyatomic, 594. 
Aconitine, 768. 
Acraldehyde, 566. 
Acridine, 752. 
Acrolein, 529, 566. 
Adenine, 788. 
Adipoeere, 565. 
Affinity, 21. 
Air, 73. 

composition of, 73. 

dew-point, 85. 
Alabaster, 328. 
Alanine, 604. 
Albite, 384. 
Albumen, 774. 
Albuminoid matters, 770. 
Albumoids, 774. 
Albumoses, 773. 
Alcohol radicals, 458. 
Alcohol, allyl, 528. 

amyl, 524. 

active, 526. 
fermentation, 524. 
normal, 524. 
tertiary, 527. 

benzyl, 702. 

butyl, 522. 

fermentation, 522. 
normal, 523. 
secondary, 523. 
tertiary, 523. 

cetyl, 528. 

cinnamic, 731. 

ethyl, 498. 

heptyl, 527. 

hexyl, 527. 

isopropyl, 522. 

methyl, 485. 

octyl, 527. 

propyl, 522. 
Alcohols, dihydric, 462, 577. 

monohydric, 450, 483, 549. 

polyhydric, 460, 633. 

primary, secondary, tertiary, 
521. 
Aldehyde, acetic, 553. 

polymerides of, 555. 

anisic, 711. 

cinnamic, 730. 

crotonic, 554, 567. 

formic, 545. 

salicylic, 708. 
Aldehydes, 453. 
Aldehydine, 750. 
AldoL 554. 



67 



794 



INDEX. 



Aliphatic series, 662. 
Alizarin, 743. 
Alkaloids, 752. 
Allantoin, 628. 
Alloxan, 626. 
Alloxantin, 628. 
Alloys, 57, 248. 

table of, 249. 
AUyl alcohol, 628. 

bromide, 573. 

iodide, 529. 

sulphide, 529. 

sulphocyanate, 529. 

tribromide, 529. 
Allylene, 576. 
Alum, 382. 
Aluminite, 383. 
Aluminium, 380. 

chloride, 381. 

oxide, 381. 

silicates, 384. 

sulphate, 382. 
Amalgams, 57. 
Amblygonite, 315. 
Amelide, 472. 
Amides, 454. 
Amidoazobenzene, 688. 
Amidobenzene, 683. 
Amidonaphthalene, 739. 
Amidothiophene, 746. 
Amines, 455, 530. 

nitroso, 531. 
Ammonia, 149. 

action of CI and I, 154. 

action of potassium, 155. 

alum, 383. 

combustion of, 153. 

composition, 151. 

in air, 79, 

in gas liquor, 157. 

liquefaction, 150. 

-water, 151. 
Ammonias, compound, 455, 530. 
Ammonium acetate, 550. 

amalgam, 155. 

carbamate, 159. 

carbonate, 158. 

chloride, 156. 

formate, 544. 

isocyanate, 475. 

molybdate, 414. 

nitrate, 158. 

oxalate, 608. 

oxalurate, 629. 

purpurate, 628. 



Ammonium sulphate, 159. 

sulphide, 157. 

sulphocyanate, 482. 

sulphydrate, 157. 

theory of, 156. 
Ampere's theory, 40. 
Amygdalin, 657. 
Amyl alcohols, 524. 

chloride, 526. 

iodide, 626, 

nitrite, 526. 

oxide, 626. 
Amylenes, 674. 

bromides, 575. 

polymerides of, 575. 
Amyloid, 666, 773. 
Anatase, 421. 
Anhydrite, 328. 
Anil, 695. 
Anilides, 684. 
Aniline, 683. 

colors, 691. 

hydrochloride, 684. 

oxalate, 684. 

salts, 684. 
Anisic aldehyde, 712. 

compounds, 711. 
Anisol, 680. 
Anorthite, 384. 
Anthracene, 741. 
Anthracite, 212. 
Anthrapurpurin, 745. 
Anthraquinone, 742. 
Antifebrin, 684. 

Antimonio-potassium tartrate, 618. 
Antimony, 195. 

antimonate, 198. 

oxide, 197. 

pentachloride, 197. 

pentasulphide, 200. 

pentoxide, 199. 

trichloride, 196. 

trioxide, 198. 

trisulphide, 199. 
Antipyrine, 676, 770. 
Apomorphine, 765. 
Aposepedine, 604. 
Aquamarine, 333. ^ 
Aqua-regia, 170. 
Arabinose, 636, 654. 
Arbutin 657. 
Argentite, 320. 
Argon, 77. 

in air, 73* 
Argyrodite, 422. 



INDEX. 



795 



Aromatic compounds, 662. 

isomerism of, 665. 
Arragonite, 327. 
Arrhenius's theory, 276. 
Arsenic, 186. 

chloride, 189. 

disulphide, 193. 

fluoride, 189. 

pentasulphide, 194. 

pentoxide, 192. 

tests for, 190. 

trioxide, 189. 

trisulphide, 193, 
Arsine, 188. 
Arsines, 466. 
Aseptol, 683. 
Asparagin, 613. 
Assay, dry, 322. 

wet, 323. 
Assimilation, 782. 
Atmospheric air, 73. 
Atomic heats, 44. 

theory, 37. 

weights, 49. 

determination of, 41-47. 
Atomicity, theory of, 232-234, 291. 
Atoms, 23, 36. 
Atropine, 755. 
Auric chloride, 375. 
Aurin, 692. 
Aurous chloride, 375. 
Australene, 720. 
Avogadro's law, 42. 
Azobenzene, 663, 675. 
Azoxybenzene, 675. 
Azure blue, 401. 
Azurite, 361. 

Barium, 331. 

carbonate, 333. 

chloride, 332. 

dioxide, 332. 

hydrate, 332L 

nitrate, 332. 

oxide, 331. 

sulphate, 333. 

sulphide, 332. 

tests, 333. 
Bassorin, 654. 
Beer, 649. 
Benzalchloride, 700. 
Benzalazine, 704. 
Benzaldehyde, 703. 
Benzamide, 705, 707. 
Benzene, 671. 



Benzene addition compounds, 672. 

azoderivatives, 674. 

azoxy-, 675. 

constitution of, 667. 

dibromo-, 673. 

dichloro-, 673. 

dinitro-, 674. 

hexachloro-, 673. 

hydrazo-, 675. 

monobromo-, 673. 

monochloro-, 673. 

nitro-, 674. 

substitution compounds, 672. 

sulphone, 677. 
Benzidine, 675. 
Benzil, 705. 
Benzine, 520. 
Benzoin, 704. 
Benzol, 671. 
Benzonitrile, 677. 
Benzophenone, 707. 
Benzoyl chloride, 705. 
Benzotrichloride, 700. 
Benzyl alcohol, 702. 

chloride, 699, 703. 
Benzylamine, 703. 
Berthollet's laws, 277. 
Beryl, 333. 
Beryllium, 333. 
Bessemer process, 395. 
Bilirubin, 786. 
Biliverdin, 787. 
Binary compounds, 50. 
Bismuth, 377. 

chloride, 378. 

nitrate, 379. 

oxide, 378. 

tests, 379. 
Bituminous coal, 212. 
Biuret, 481. 
Bleaching, chlorine, 125. 

-liquids, 133. 

-powder, 123, 328. 

sulphur dioxide, 110. 
Blende, 337. 
Blue vitriol, 359. 
Boiling-points, determination of, 

445. 
Bone-oil, 747. 
Borax, 313. 
Boron, 201. 

chloride, 202. 

crystallized, 202. 

fluoride, 203. 

oxide, 203. 



796 



INDEX. 



Boro-potassium tartrate, 619. 
Brauite, 405. 
Bromine, 137. 

oxides, 139. 
Bromobenzenes, 673. 
Bromoform, 490. 
Bromopicrin, 492. 
Bronze, 361. 
Brookite, 421. 
Brucine, 762. 
Bunsen burner, 231. 
Butaldehyde, 563. 
Butane, 498, 519. 
Butyl alcohols, 522. 
Butylenes, 573. 
Butyrone, 663. 

Cacodyl, 496. 
Cadaverine, 584. 
Cadmics, 342. 
Cadmium, 342. 

iodide, 342. 

oxide, 342. 

sulphate, 343. 

sulphide, 342. 
Caesium, 315. 
CaflFeidine, 769. 
Caffeine, 768. 
Calamine, 337. 
Calcite, 327. 
Calcium, 324. 

butyrate, 563. 

carbide, 326. 

carbonate, 327. 

chloride, 326. 

-freezing mixture, 271. 

hydrate, 325. 

hypochlorite, 329. 

lactate, 600. 

nitrate, 327. 

oxide, 325. 

saccharate, 643. 

sulphate, 328. 

tests, 330. 
Calomel, 366. 
Camphenes, 659. 
Camphor, 724. 

artificial, 722. 

Borneo, 726. 

mint, 726. 

thyme, 718. 
Camphorone, 728. 
Camphoroxime, 725. 
Camphors, 718. 
Candles, 592. 



Caoutchouc, 723. 
Caramel, 643. 
Carbamide, 474, 477. 
Carbimide, 475. 
Carbinol, 522. 
Carbon, 210. 

compounds, 429. 

classification of, 435. 
saturated, 430. 

dioxide, 219. 

in air, 77, 79. 
liquefaction, 222. 

disulphide, 225. 

estimation of, 436. 

monoxide, 217. 

compounds of, 473. 

oxysulphide, 226. 

sesquichloride, 571. 

tetrachloride, 489, 492. 
Carbonates, 287. 

tests for, 289. 
Carbonyl chloride, 219. 
Carborundum, 216. 
Carbylamines, 493, 514. 
Carvacrol, 718. 
Casein, 781. 
Cassiterite, 416, 418. 
Catechol, 693. 
Cedrene, 723. 
Celestite, 331. 
Celluloid, 657. 
Celluloses, 635, 654. 
Cement, 326. 

copper, 355. 
Cerite, 385. 
Cerium, 385. 
Cerusite, 352. 
Ceryl alcohol, 528. 
Cetyl alcohol, 528, 
Chalk, 327. 
Chalkosine, 354. 
Charcoal, 212. 

absorbent properties of, 214. 

animal, 214. 

reduction by, 215. 

wood, 212. 
Chemical energy, 240, 
Chloral, 556. 
Chloranile, 695. 
Chlorethylene, 570. 
Chlorhydrins, 587. 
Chlorides, 258. 

monatomic, 448. 

of acid radicals, 454, 

of sulphur, 136, 



INDEX. 



797 



Chlorine, 122. 

analogies, with Br and I, 145, 

bleaching by, 125. 

disinfection by, 125. 

group, analogies of, 145. 

liquefaction, 124. 

manufacture of, 123. 

oxides, 131. 

peroxide, 134. 
Chlorobenzenes, 673. 
Chloroform, 489. 
Chloropicrin, 491. 
Cholesterin, 784. 
Choline, 784. 
Chondrin, 782. 
Chromates, 412. 
Chrome alum, 412. 

iron, 410. 

yellow, 353. 
Chromium, 410. 

chlorides, 413. 

oxides, 411. 

oxychloride, 413. 
Cinchona bark, 758. 
Cinchonicine, 758. 
Cinchonidine, 758. 
Cinchonine, 761. 
Cineol, 726. 
Cinnabar, 362, 365. 
Cinnamic alcohol, 731. 

aldehyde, 730. 
Clay, 384. 
Cleveite, 410. 
Coal, 212. 
Cobalt, 401. 

chloride, 402. 

glance, 401. 

oxides, 401. 

sulphate, 402. 

tests, 402. 
Cocaine, 757. 
Codeine, 766. 

Coefficient of solubility, 67. 
Cohesion, 21, 25. 
Coke, 212. 
Colcothar, 397. 
Collidines, 750. 
Collodion, 657. 
Columbite, 371. 
Combination, 18, 23. 

laws of, 33, 37. 
Combustion, slow, 68. 
Conhydrine, 754. 
Coniferin, 659. 
Conine, 753. 



Copper, 354. 

acetates, 549. 

alloys, 358, 361. 

atomicity of, 370. 

carbonates, 361. 

chlorides, 359. 

formate, 544. 

glance, 358. 

oxides, 358. 

pyrites, 354. 

sulphates, 360. 

sulphides, 358. 

tests, 362. 
Coralline red, 692. 
Corrosive sublimate, 367. 
Corundum, 381. 
Cotarnine, 767. 
Creatine, 632. 
Creatinine, 632. 
Cresols, 700. 

Critical temperature, 61. 
Crocoite, 410. 
Crotonaldehyde, 567. 
Cryolite, 312. 
Crypton, 80. 

Crystallization, water of, 270. 
Cubebene, 723. 
Cumene, 717. 
Cuminol, 717. 
Cupellation, 318, 322. 
Cyamelide, 474. 
Cyanamide, 471. 
Cyanides, 467. 
Cyanobenzene, 677. 
Cyanogen, 463. 

bromide, 471. 

chlorides, 470. 

compounds, 462. 

iodide, 471. 
Cymene, 717. 

Dalton's laws, 33, 36. 
Dambonite, 729. 
Daturine, 756. 
Decomposition, 23, 27, 30. 
Definite proportions, law of, 31. 
Dew-point, 85. 
Dextrin, 651. 
Diacetyl, 557. 
Diamines, 461. 
Diamond, 211. 

combustion of, 220. 
Diastase, 649, 652. 
Diazoacids, 605. 
Diazoamidobenzene, 687. 



67* 



798 



INDEX. 



Diazobenzene compounds, 686. 
Diazocompounds, 664. 
Dibenzoyl, 705. 
Dichlorethane, 607. 
Dichlorether, 505. 
Dichlorethylene, 570. 
Dichlorhydrins, 688. 
Didymium, 385. 
Diethyl, 498. 
Diethylamine, 535. 
Diethylphosphine, 536. 
Digitalin, 659. 
Dihydrocymene, 723. 
Diketones, 454. 
Dimethyl, 498. 
Dimethylacetal, 583. 
Dimethylamine, 534. 
Dimethyl-aniline, 685. 
Dimethylarsine, 496. 
Dimethylbenzenes, 714. 
Dimethylethylenes, 673. 
Dimorphism, 100. 
Dinitrobenzenes, 674. 
Dioxindol, 737. 
Dioxybenzenes, 692. 
Diphenyl, 672, 673. 
Diphenylamine, 685. 

blue, 686. 
Diphenylketone, 707. 
Dipyridine, 749. 
Disspciation, 86. 
Disulphones, 582. 
Dobereiner's lamp, 500. 
Dolomite, 336. 
Ductility, 245. 
Dulcitol, 634. 
Dutch liquid, 570.. 

Ecgonine, 758. 
Edisonite, 421. 
Efflorescence, 2701, 
Ekasilicon, 422. 
Elaidin, 592. 
Electrolysis, 274. 

of water, 80. 

laws of, 276. 
Elementary analysis, 436. 
Elements, 20, 23. 

table of, 49. 
Emerald, 333. 
Emery, 381. 
Emulsin, 658. 

Endothermic compounds^ 242. 
Eosin, 716. 
Epichlorhydrin, 589. 



Epsom salt, 336. 
Equivalence, 234. 
Erbium. 388. 
Erythritol, 633. 
Esculin, 657. 
Ethane, 498. 
Ether, 602. 

acetoacetic, 551. 

Kay's, 489. 

cenanthylic, 648. 

pelargonic, 648. 
Etherification, theory of, 503. 
Ethers, compound, 452, 498. 

cyanuric, 517. 

nitrous, 510. 

phosphoric, 514. 

simple, 497. 
Ethyl acetate, 550. 

acetoacetate, 551. 

borate, 514. 

bromide, 507. 

carbamate, 515. 

carbonate, 516. 

carbylamine, 509. 

chloride, 506. 

chlorocarbonate, 516. 

cyanate, 508. 

cyanide, 608. 

cyanurate, 517. 

diazoacetate, 605. 

hydroxide, 498. 

iodide, 506. 

isocyanate, 516. 

malonate, 609. 

nitrate, 511. 

nitrite, 609. 

orthocarbonate, 515. 

oxalate, 608. 

oxide, 602. 

phosphates, 514. 

silicates, 514. 

sulphates, 512. 

sulphide, 505. 

sulphite, 512. 

sulphurous chloride, 513. 

sulphydrate, 606. 
Ethylallyl, 676. 
Ethylamine, 634. 

hydrochloride, 534. 
Ethylates, 601. 
Ethylene, 668. 

acetates, 580. 

bromhydrate, 680. 

bromide, 670. 

chlorhydrate, 579. 



INDEX. 



799 



Ethylene, chloride, 570. 

chloro-derivatives, 570. 

diamines, 584. 

hydrate, 578. 

iodide, 570. 

nitrates, 580. 

oxide, 581. 

bases from, 582. 
Ethylethylene, 574. 
Ethylhydrazine, 532. 
Ethylidene chloride, 554. 

cyanide, 612. 

glycol, 582. 
Ethyl-phenyl oxide, 680. 
Ethylphosphines, 536. 
Ethylvinyl, 574. 
Eudiometric synthesis, 82. 
Euxenite, 371, 389, 409. 
Exothermic compounds, 242. 

Faraday's law, 276. 
Fats, natural, 590. 
Fatty series, 662. 
Feldspar, 384. 
Fenchene, 722. 
Fenchone, 726. 
Fenchoneoxime, 726. 
Fergusonite, 371. 
Fermentation, 646. 

acetic, 547. 

alcoholic, 646. 

butyric, 647. 

lactic, 597, 647. 

viscous, 648. 
Ferric acetate, 550. 

chloride, 398. 

ferrocyanide, 469. 

oxide, 397. 

sulphate, 400. 
Ferricyanides, 469. 
Ferrocyanides, 468. 
Ferro-potassium tartrate, 619. 
Ferrosoferric oxide, 397. 
Ferrous carbonate, 400. 

chloride, 398. 

ferricyanide, 470. 

lactate, 600. 

oxide, 396. 

sulphate, 399. 
Fibrins, 773, 776. 
Fire, 68. 

-damp, 484. 
Flame, 68, 228. 
Flavopurpurin, 745. 
Fluorescein, 715. 



Fluorine, 146. 

Formaldehyde, 545. 

Formates, 544. 

Formonitrile, 466, 544. 

Formose, 545. 

Formula, chemical, 48. 

Formulae, constitutional, empirical, 

rational, 452. 
Freezing mixture, 271. 
ii^o/ing-points, determination of, 

444. 
Fructose, 639. 
Fuchsine, 689. 
Fulminates, 495. 
Furfurane, 745. 
Furfurol, 745. 
Fusel oil, 525. 
Fusible metal, 248. 

Gadolinite, 388. 

Galactose, 639. 

Galena, 343, 349. 

Gallium, 386. 

Galvanized iron, 339. 

Garnet, 384. 

Garnierite, 403. 

Gases, molecular volume of, 42„ 

Gasoline, 520. 

Gay-Lussac's laws, 37. 

Gelatin, 781. 

Gelatinoids, 774. 

Germanium, 422. 

German silver, 361. 

Gilding, 376. 

Glass, 210. 

etching on, 147. 

soluble, 209. 
Glauber's salt, 309. 
Globulins, 773, 776. 
Glucinum, 333. 

chloride, 334. 

oxide, 334. 
Glucose, 637. 

tests for, 638. 
Glucosides, 657. 
Gluten, 650. 
Glycerides, 690. 
Glycerol, 586. 

ethers of, 587, 590„ 
Glycide, 689. 
Glycine, 602. 
Glycocoll, 602. 
Glycocyamidine, 631. 
Glycocyamine, 631. 
Glycogen, 653. 



800 



INDEX. 



Glycol, 678. 

ethers of, 579. 
GlycoUide, 595. 
Glycols, 460, 577. 

propylene, 586. 
Glycolyl urea, 630. 
Glyoxal, 596. 
Glyoxime, 596. 
Goethite, 397. 
Gold, 373. 

assay, 376. 

chlorides, 376. 

oxides, 375. 
Goulard's solution, 549. 
Graphite, 211. 
Guaiacol, 693. 
Guanidine, 472. 

derivatives of, 63L 
Guanine, 788. 
Gum arabic, 654. 

tragacanth, 654. 
Gums, 653. 
Gun-cotton, 656. 
Gunpowder, 302. 

nitro, 657. 
Gutta-percha, 723. 
Gypsum, 328. 

Hardness, scale of, 789. 
Hausmannite, 405. 
Heavy spar, 333. 
Helium, 410. 
Hematin, 780. 
Hematite, 390. 
Hematoidin, 780. 
Hemimellithene, 717. 
Hemoglobin, 778. 
Hexachlorethane, 507. 
Hexahydrobenzene, 672. 
Hexamethylbenzene, 664. 
Holmium, 389. 
Homologous bodies, 435. 
Horn silver, 320. 
Hydantoin, 630. 
Hydrates, 52, 53. 
Hydrazine, 160. 
Hydrazines, 532. 

aromatic, 676. 
Hydrazobenzene, 675. 
Hydrocarbons, C^R^^+'^y 517. 

C"H2^ 571. 

C°H2n-2, 575. 

formation of, 433. 

structure, 434. 
Hydrocinchonine, 761. 



Hydrogen, 58. 

absorption by palladium, 61, 64, 

antimonide, 196. 

arsenide, 188. 

carbide in air, 80. 

chemical properties, 61. 

dioxide, 95. 

estimation of, 436. 

liquefaction, 60. 

occlusion of, 61. 

persulphide, 105. 

phosphide, 175. 

physical properties, 60. 

preparation, 59. 

silicide, 205. 

sulphide, 102. 
Hydrogenium, 61. 
Hydroquinone, 693. 
Hydroxides, 53, 87. 
Hydroxyethylene amines, 582. 
Hydroxyl, 116. 
Hydroxylamine, 159. 
Hyoscine, 756. 
Hyoscyamine, 756. 
Hypnone, 707. 

Hypochlorous anhydride, 132, 
Hypoxanthine, 788. 

Idoerase, 384. 
Igasurine, 762. 
Indican, 733. 
Indiglucin, 733. 
Indigo, 732. 

carmine, 733, 

syntheses of, 734. 

white, 735. 
Indium, 387. 
Indol, 737. 
Indophenin, 736. 
Indoxyl, 734. 
Ink, 401, 660. 

sympathetic, 402. 
Inosite, 729. 
Inulin, 653. 
Iodine, 140. 

oxides, 144. 

test for, 142. 
Iodoform, 490. 
lodol, 747. 
Iridium, 428. 
Iron, 389. 

carbonate, 400. 

cast, 394. 

chlorides, 398. 

lactate, 600. 



INDEX. 



801 



Iron oxides, 396. 

passive, 169, 394. 

soft, 393. 

sulphates, 399. 

sulphides, 398. 

tests, 400, 401. 
Isatin, 736. 
Is ethionamide, 585. 
Isomaltose, 645. 
Isomerism, 445. 

of position, 668. 

of the benzene derivatii 
Isomorphism, 47, 267. 
Isoprene, 720, 723. 
Isopropyl alcohol, 522. 

iodide, 522. 
Isopropylbenzene, 717. 
Isopropylethylene, 575. 
Isoquinoline, 751. 
Isuret, 480. 

Jet, 212. 

Kairine, 770. 
Kaolin, 384. 
Kay's ether, 489. 
Kerosene, 520. 
Ketones, 453. 
Kieserite, 336. 
Kupfemickel, 403. 

Labradorite, 384. 
Lactamide, 600. 
Lactates, 600. 
Lactose, 644. 
Lamp-bla<3k, 213. 
Lanthanum, 385. 
Lead, 343. 

acetates, 549. 

argentiferous, 345. 

atomicity of, 343. 

carbonate, 352. 

chloride, 350. 

chromate, 353. 

dioxide, 348. 

formate, 544, 

iodide, 350. 

monoxide, 347. 

nitrate, 351. 

red oxide, 348. 

sulphate. 351. 

sulphide, 349. 

tests, 353. 

white, 353. 
Lecithine, 582, 784. 



665. 



Lepidolite, 315. 
Leucine, 565, 604. 
Leucite, 384. 
Leucoline, 750. 
Leucorosaniline, 690, 
Levulosan, 640. 
Levulose, 639. 
Lignite, 212. 
Lime, 325. 

chlorinated, 328. 

hydraulic, 325. 
Liquation, 248. 
Litharge, 346, 347. 
Lithium, 315. 
Lithographic stone, 327, 
Lunar caustic, 322. 
Lutidines, 750. 
Lyons blue, 691. 

Magenta, 689. 
Magnesite, 336. 
Magnesium, 334. 

carbonate, 336. 

chloride, 336. 

citrate, 622. 

oxide, 335, 

sulphate, 337. 

tests, 337. 
Magnetite, 397. 
Malachite, 361. 

green, 685, 700. 
Malamide, 613. 
Malleability, 245. 
Malonyl urea, 627. 
Maltose, 645. 
Manganese, 405. 

carbonate, 408. 

dioxide, 406. 

oxides. 405. 

steel, 405. 

sulphate, 407. 

tests, 408. 
Mannitan, 634. 
Mannitol, 634. 
Mannose, 686. 
Marble, 327. 
Marcasite, 398. 
Marl, 384. 
Marsh gas, 484. 
Marsh's apparatus, 191. 
Massicot, 347. 
Matches, 175. 
Meconine, 767, 
Melamine, 472. 
Melezitose. 646. 



802 



INDEX. 



Melitose, 645. 

Melting-points, determination of, 

444. 
Mendelejeff's periodic theory, 294. 
Menthene, 727. 
Menthol, 726. 
Mercaptan, 605. 
Mercur-ethyl, 539. 
Mercuric chloride, 367. 

iodide, 368. 
Mercur-methyl, 639. 
Mereurous chloride, 366. 

iodide, 368. 
Mercury, 362. 

atomicity of, 370. 

cyanide, 467. 

fulminate, 495. 

nitrates, 369. 

oxides, 364. 

sulphates, 369. 

sulphide, 364. 

tests, 370. 
Mesitylene, 716= 
Mesoxalyl-urea, 626. 
Metacetone, 644. 
Metaldehyde, 555. 
Metallic carbonates, 287. 

chlorides, 258. 

hydrates, 260, 256. 

nitrates, 283. 

oxides, 250. 

chemical properties of, 253. 
classification of, 251. 

sulphates, 286. 

sulphides, 267. 
Metals, 243. 

classification of, 289, 296. 

diatomic, 290. 

general properties of, 243. 

monatomic, 290. 

natural state and extraction, 
247. 

tetratomic, 293. 
Metamerism, 446. 
Metastyrolene, 730. 
Metaxylene, 714. 
Methane, 484. 
Methylacetylene, 576. 
Methylal, 488. 
Methylamine, 533. 

hydrochloride, 533. 
Methylaniline, 685. 
Methylarsines, 497. 
Metbylbenzene, 697. 
Methyl bromide, 487. 



Methyl carbylamine, 493, 

chloride, 487. 

compounds, 483. 

cyanide, 492. 

cyanurate, 517. 

hydroxide, 485. 

iodide, 487. 

nitrate, 493o 

nitrite, 493. 

oxalate, 486, 608. 

oxide, 487. 

salicylate, 710. 
Methylchloracetol, 558. 
Methylene chloride, 488. 

diacetate, 489. 

diethylate, 488. 

iodide, 488. 
Methylethyl oxide, 502. 
Methylglycocoll, 603. 
Methylmorphine, 766. 
Methylphenyl ketone, 707. 
Methylphenyl oxide, 680. 
Mica, 384. 
Millerite, 403. 
Millon's reagent, 771. 
Mineral waters, 92. 
Minium, 348. 
Molecular structures, 237. 

weights, determination of, 41 
440. 
Molecules, 21. 
Molybdenite, 414. 
Molybdenum, 414. 
Monazite, 385, 423. 
Monochlorether, 505, 
Monochlorhydrin, 587. 
Morphine, 764. 
Mortar, 326. 
Mucilages, 653. 
Murexide, 625, 628. 
Mycose, 645. 
Myosin, 777. 

Naphtha, 620. 
Naphthalene, 671, 738 
Naphthols, 740. 
Naphthylamines, 741.. 
Narceine, 764. 
Narcotine, 767. 
Neurine, 582, 784. 
Neodymium, 385. 
Nickel, 403. 

chloride, 404. 

glance, 40.3. 

oxides, 403. 



INDEX. 



803 



Nickel plating, 403. 

steel, 403. 

sulphate, 404. 

tests, 404. 
Nicotine, 754. 
Night green, 691. 
Niobium, 371. 

chlorides, 372. 

oxides, 372. 
Nitrates, 283. 

tests for, 284. 
Nitric anhydride, 167. 

oxide, 163. 
Nitrobenzene, 674. 
Nitroethane, 509. 
Nitroferrocyanides, 470. 
Nitroform, 491. 
Nitrogen, 148. 

chloride, 154. 

estimation of, 439. 

group of elements, 200. 

hydrogen, compounds of, 149. 

in air, 73-77. 

iodide, 155. 

monoxide, 161. 

oxides, 160. 

pentoxide, 167. 

peroxide, 165. 

trioxide, 164. 
Nitroglycerin, 590. 
Nitromethane, 493. 
Nitronaphthalene, 738. 
Nitrophenols, 680. 
Nitro-powders, 657. 
Nitroso-amines, 685. 
Nitrosodimethylaniline, 685. 
Nitrosomethylaniline, 685. 
Nitrosophenol, 681. 
Nitrosyl-chloride, 171. 
Nitrothiophene, 746. 
Nitrotoluenes, 700. 
Nitryl, chloride and bromide, 166. 
Nomenclature, 47. 
Nornarcotine, 767. 
Notation, 47-57. 

Occlusion, 61. 
(Enanthic ether, 648. 
Oils, essentia], 718. 

fatty and drying, 592. 
Olein, 591. 
Oolitic iron, 389. 
Opium, 763. 
Orangeite, 423. 
Orcein, 701. 



Orcinol, 701. 

Organo-metallic compounds, 456, 

539. 
Orpiment, 193. 
Orthite, 389. 
Orthoxylene, 714. 
Osmium, 428. 
Oxalates, 606. 
Oxalyl-urea, 629. 
Oxamide, 608. 
Oxides, 50, 251. 

acid, 251. 

antimonic, 199. 

antimonous, 198. 

arsenic, 192. 

arsenious, 189. 

basic, 251. 

boric, 204. 

chlorocarbonic, 219. 

chlorous, 133. 

cupric, 358. 

cuprous, 357. 

ferric, 397. 

ferroso-ferric, 397. 

ferrous, 396. 

hypochlorous, 132. 

manganic, 405. 

man^anoso-manganic, 405. 

mercuric, 364. 

mercurous, 364. 
■ metallic, 250, 

classification of, 251. 

molybdic, 414, 

niobic, 372. 

nitric, 163. 

nitrous, 161. 

persulphuric, 120. 

phosphoric, 183. 

plumbic, 347. 

plumboso-plumbic, 348. 

saline, 251. 

silicic, 208. 

singular, 251. 

stannic, 418. 

stannous, 418. 

sulphuric, 110. 

sulphurous, 107. 

tantalic, 372. 

vanadic, 370. 
Oxindol, 737. 
Oxygen, 64. 

in air, 73. 

liquefaction, 67. 

manufacture, 66. 

preparation, 65. 



804 



INDEX. 



Oxygen properties, 66. 
Oxyhemoglobin, 779. 
Oxyhydrogen blowpipe, 69. 
Oxyphenols, 693. 
Ozone, 69, 

composition, 72. 

formation, 70. 

in air, 80. 

properties, 71. 

tests for, 69. 

Palladium, 427. 
Palmitin, 591. 
Papaverine, 764. 
Paracetphenetidine, 769. 
Paraeyanogen, 463. 
Paraffin, 620. 
Paraldehyde, 555. 
Pararosaniline, 690. 
Paraxylene, 714. 
Parchment paper, 656. 
Paris violet, 691. 
Pectic matters, 662. 
Pelargonic ether, 648. 
Pentachlorethane, 507. 
Pentamethylene diamine, 584. 
Pentenes, 674. 
Pepsin, 778. 
Peptones, 773. 
Perchloraldehyde, 505. 
Perchlorether, 506. 
Perkins's reaction, 731, 
Perseitol, 635. 
Petroleum, 520. 

ether, 520. 
Phellandrene, 723. 
Phenacetin, 770. 
Phenanthrene, 742. 
Phenetidines, 769. 
Phenetol, 680. 
Phenol, 677. 

ethers of, 680. 
Phenols, 664. 
Phenyl cyanide, 677. 

nitro-, 680. 

nitroso-, 680. 

oxide, 680. 
Phenylacetylene, 732. 
Phenylamine, 683. 
Phenylhydrazine, 554, 676. 
Phenylhydrazones, 554. 
Phenyllactosazone, 645. 
Phenylmaltosazone. 645. 
Phenylmethane, 697. 
Phloretin, 659. 



Phloridzin, 659. 
Phloroglucinol, 696. 
Phosgene gas, 219. 
Phosphine, 179. 
Phosphines, 456. 
Phosphonium, 177. 
Phosphoric anhydride, 183. 

ethers, 514. 
Phosphorus, 171. 

amorphous, 173. 

bromide, 179. 

iodide, 180. 

oxides, 180. 

oxychloride, 179. 

pentachloride, 178. 

pentoxide, 183. 

poisonous properties, 174. 

sulphides, 186. 

sulphochloride, 179. 

trichloride, 178. 
Phthaleins, 715. 
Phthalic anhydride, 715. 
Picolines, 750. 
Pinacolin, 558. 
Pinacone, 558, 578. 
Piperidine, 748, 750. 
Piperine, 765. 
Pitchblende, 409, 
Plaster of Paris, 328. 
Platinum, 424. 

black, 62, 425. 

chlorides, 426. 

sponge, 425. 
Plumbago, 211. 
Polymerism, 445. 
Populin, 658. 
Porcelain, 384. 
Potash, caustic, 288. 
Potassamide, 155. 
Potassium, 297. 

acetate, 548. 

acid carbonate, 305. 

acid sulphate, 303. 

amide, 155. 

bromide, 301. 

carbonate, 304. 

chlorate, 303. 

chloride, 300. 

chromate, 412. 

cyanate, 475. 

cyanide, 467. 

dichromate, 412. 

ethylate, 501. 

ferricyanide, 469. 

ferrocyanide, 468. 



INDEX. 



805 



Potassium hydroxide, 298. 

iodide, 300. 

isocyanate, 474. 

manganate, 406. 

methylate, 486. 

nitrate, .301. 

oxalates, 607, 608. 

oxides, 298. 

perchlorate, 304. 

permanganate, 407. 

pierate, 682. 

sulphate, 303. 

sulphides, 299. 

sulphocyanate, 482. 

tartrates, 618. 

tests, 305. 

thiocyanate, 482. 
Pottery, 384. 

lead glazing, 349. 
Praseodymium, 386. 
Propenyl tribromide, 589. 

trinitrate, 590. 
Proprionitrile, 508. 
Propyl alcohol, 522. 

iodide, 522. 
Propylene glycols, 586. 
Propylenes, 573. 
Propylethylene, 675. 
Proteids, 770. 
Prussian blue, 401, 469. 
Pseudocumene, 717. 
Purine, 788. 
Purple of Cassius, 376. 
Purpurin, 744. 
Putrescine, 584. 
Pyridic bases, 747. 
Pyridine, 749. 
Pyrite, 398. 
Pyrocatechin, 693. 
Pyrochlorite, 371. 
Pyrogallol, 713. 
Pyrolusite, 406. 
Pyroxylin, 656. 
Pyrrol, 747. 
Pyrrolidine, 747. 
Pyrroline, 747. 

Quercite, 729. 
Quercitrin, 657. 
Quinaidine, 751. 
Quinhydrone, 694. 
Quinicine, 768. 
Quinidine, 768. 
Quinine, 769. 
Quinoline, 760. 



Quinone, 694. 

dioxime, 696. 
monoxime, 681, 696. 

Radicals, diatomic, 460. 

monatomic, 448, 468. 

polyatomic, 469. 
Rare earths, 388. 
Raffinose, 645. 
Realgar, 193. 
Red precipitate, 364. 
Resorcinol, 693. 
Respiration, 69, 783. 
Rhamnose, 636. 
Rhodium, 427. 
Richter's laws, 265. 
Rochelle salt, 618. 
Rosaniline, 689. 

colors, 691. 
Rubidium, 315. 
Ruby, 381. 
Ruthenium, 427. 
Rutile, 421. 

Saccharin, 638. 
Saccharose, 640. 
Safety-lamp, 229. 
Salicin, 658. 
Salicyl aldehyde, 708. 
Saligeninol, 658, 708. 
Saliretin, 658. 
Saltpetre, 302. 

Chili, 302. 
Salts, 53, 262. 

action of acids, 277. 

bases, 279. 

electricity, 274. 

heat, 273. 

metals, 276. 

salts, 280, 282. 

water, 268. 
etflorescent, 270. 
neutral, acid and basic, 264. 
Samarium, 389. 
Samarskite, 389. 
Sandmeyer's reaction, 687. 
Saponification, 593. 
Sapphire, 381. 
Sarcine, 788. 
Sarcosine, 603, 632. 
Satin spar, 328. 
Saturated hydrocarbons, 517. 
Scandium, 389. 
Scheelite, 414. 
Selenium, 121. 
Silica, 208. 



806 



INDEX. 



I'' 



Silica, soluble, 210. 
Silicon, 204. 

chloride, 206. 

crystallized, 205. 
fluoride, 207. 

oxide, 208. 
Silicon-ethy], 538. 
Silver, 317. 

acetate, 550. 

assay, 322. 

chloride, 320. 

cupellation, 318. 

fulminate, 495. 

fulminating, 320. 

iodide, 321. 

metallurgy of, 317. 

nitrate, 321. 

oxide, 320. 

Patio process, 318. 

spitting of, 319. 

sulphide, 320. 

tests, 322. 

AVashoe process, 318. 
Silvering, 322. 
Skatol, 738. 
Slow combustion, 68. 
Smalt, 401. 
Smaltite, 401. 
Smithsonite, 337. 
Soap, 593. 

Sodio-potassium tartrate, 616. 
Sodium, 306. 

acetate, 549. 

acid carbonate, 313. 

acid sulphate, 310. 

borate, 313. 

carbonate, 310. 

chloride, 308. 

dioxide, 307. 

ethylate, 501. 

hydracrylate, 601. 

hydrate, 307. 

hydrazoate, 160. 

hydrosulphite, 110. 

hyposulphite, 110. 

manufacture of, 306. 

Castner's process, 307. 
Deville's process, 306. 
Netto's process, 307. 

nitrofeiTOcyanide, 470. 

oxides, 307. 

phosphates, 313. 

sulphate, 309. 

sulphide, 308. 

sulphydrate, 308. 



Sodium tests, 314. 

thiosulphate, 119. 

tungstate, 415. 

uranate, 409. 
Solubility, coefficient of, 67. 
Solution, 89, 268. 

saturated, 269. 
•Sorbinose, 640. 
Sorbitol, 634. 
Spathic iron, 390, 400. 
Specific heat, 44. 
Spectrum analysis, 315. 
Spermaceti, 528. 
Sperrylite, 424. 
Sphalerite, 337. 
Spiegeleisen, 394. 
Spodumene, 315. 
Stannethyls, 540. 
Stannodiethyl, 540. 
Stannotetrethyl, 541. 
Starch, 650. 

soluble, 652. 

mononitrate, 652. 
Starches, 635. 
Stassfurth salt, 306. 
Stearin, 591. 

candles, 592. 
Stearoptenes, 718. 
Steel, 394. 

Stereoisomerism, 614. 
Stibine, 196. 
Stibines, 456. 
Stolzite, 414. 
Strontianite, 331. 
Strontium, 330. 

carbonate, 331. 

chloride, 331. 

nitrate, 331. 

saccharate, 644. 
Strychnine, 762. 
Styracin, 731. 
Styroline, 730. 
Succinic anhydride, 611o 
Succinyl chloride, 611. 
Sugar, cane, 640. 

fruit, 639. 

grape, 637. 

inverted, 643. 

milk, 644. 
Sugars, 635. 
Sugar of lead, 649. 
Sulphates, 286. 

tests for, 287. 
Sulphides, metallic, 257. 
Sulphobenzide, 677. 



INDEX. 



m 



Sulphocarbamide, 473. 
Sulphonal, 582. 
Sulphonic acids, 664. 
Sulpho-urea, 482, 483. 
Sulphur, 98. 

analogies with oxygen, 102. 

chlorides, 136. 

dimorphism of, 100. 

dioxide, 106, 107. 

oxygen acids, 106. 

peroxide, 106, 120. 

sesquioxide, 106, 107. 

soft, 100. 

trioxide, 106, 110. 
Sulphuric anhydi-ide. 111. 
Sulphurous anhydride, 107. 
Sulphuryl chloride, 110, 116. 
Supersaturation, 271. 
Synaptase, 658. 
Syntonin, 777. 

Tannin, 659. 
Tantalite, 371. 
Tantalum, 371. 

chloride, 372. 

oxide, 372. 
Tartar-emetic, 618. 
Tartaric anhydride, 617. 
Tartrates, 618. 
Tartronyl-urea, 627. 
Taurine, 585. 
Tautomerism, 697. 
Tellurium, 121. 
Terebene, 721. 
Terpenes, 718. 
Terpin, 721. 

hydrate, 721. 
Terpinene, 723. 
Terpinolene, 723. 
Tetrachlorethane, 507. 
Tetrachlorether, 505. 
Tetrachlorethylene, 571. 
Tetramethylammonium, 534. 
Tetramethylene diamine, 584. 
Tetrethylammonium, 535. 
Thalline, 770. 
Thallium, 354. 
Thebaine, 764. 
Theine, 768. 
Theobromine, 768. 
Thermo-chemistry, 240. 
Thiophene, 672, 746. 
Thiophtene, 746. 
Thiotolene, 746. 
Thioxene, 746. 



Thorite, 389. 
Thorium, 423. 
Thulium, 389. 
Thymol, 718. 
Tin, 416. 

dichloride, 419. 

oxides, 418. 

sulphides, 419. 

tests, 421. 

tetrachloride, 420. 
Tinctures, 500. 
Tinplate, 417. 
Titanium, 421. 

dioxide, 421. 
Toluene, 697. 

chloro- 699. 

nitro- 700. 
Toluidines, 701. 
Topaz, 381. 
Trehalose, 645. 
Tribenzylamine, 703. 
Tribromhydrin, 589. 
Trichloraldehyde, 556. 
Trichlorethane, 507. 
Trichlorhydrin, 588. 
Triethylamine, 535. 
Triethylphosphine, 537. 
Trimethylamine, 534. 
Trimethylbenzenes, 716,, 
Trimethylcarbinol, 523. 
Trimethylene, 571. 
Trimethylethylene, 572. 
Trimethylrosaniline, 691. 
Trinitroacetonitrile, 493. 
Trinitroglycerol, 590. 
Trinitrophenol, 681. 
Trioxymethylene, 545. 
Triphenylrosaniline, 691. 
Triphyline, 315. 
Tropaeolines, 689. 
Trypsin, 778. 
Tungsten, 415. 
Tungstic oxide, 415. 
Turnbull's blue, 470. 
Turpentine, 720. 
Turpeth mineral, 370. 
Type metal, 196. 

chemical, 88. 
Tyrosine, 712, 772. 

Uranite, 409. 
Uranium, 409. 

chlorides, 410. 

oxides, 409. 

yellow, 409. 



BOH 



INDEX. 



Uranyl nitrate, 410. 
Urea, 477. 

Ureas, compound, 481. 
Ureides, 626. 
Urethane, 515, 516. 

Vanadinite, 370. 
Vanadium, 370. 

bronze, 371. 
Vanillin, 659. 
Verdigris, 550. 
Vermilion, 365. 
Vinegar, 545. 
Vitriol, blue, 360. 

green, 3'J9. 

white, 340. 

Water, 80. 

analysis, 81. 

charcoal filter for, 215. 

dissociation, 86. 

hard, 00. 

in air, 78. 

maximum density, 85. 

mineral, 92. 

acidulous or gaseous, 92. 

alkaline, 93. 

chalybeate, 93. 

saline, 94. 

sulphatic, 94. 

sulphur, 95. 
natural state of, 89. 
of crystallization, 270. 
properties of, 85, 86. 
reactions of, 87. 
soft, 90. 

solvent properties of, 89. 
synthesis of, 82. 



Wax, 528. 

Welsbach light, 423, 424. 

White vitriol, 340. 

lead. 352. 

precipitate, 367. 
Willemite, 337. 
Wine, 648. 
Witherite, 333. 
Wolfram, 414. 
Wood-spirit, 485. 
Wurtzite, 340. 

Xanthine, 787. 
Xylenes, 714. 
Xyloidin, 652. 
Xylose, 636, 654. 

Yeast, 590. 
Ytterbium, 389. 
Yttria, 388. 
Yttrium, 389. 
Yttrotantalite, 371. 

Zeolites, 384. 
Zinc, 337. 

chloride, 340. 

hydracrylate, 601. 

lactate, 600. 

oxide, 339. 

sulphate, 340. 

sulphide, 340. 

tests, 341. 

-ethyl, 539. 

-methyl, 589. 
Zircon, 422. 
Zirconium, 422. 



THE END. 



OCT 20 1900 



I 



